How does DNA fingerprinting works? DNA fingerprinting is a reliable method for identifying people. How DNA fingerprinting works as to do with something called the HLA system (human leukocyte antigen system). The HLA is a system that codes for proteins on the surfaces of many cells, including white blood cells. HLA genotyping is used in transplants. With this system, people could match transplant genetically, so that a transplant from one person to another wouldn’t be rejected by the recipient.
There are four different HLA genes, labeled nicely A, B, C and D. HLA A has 23 alleles. HLA B has 47. HLA C has 8 and D has 23. A person could be, for example, A11, B16, C5 and D11. With more alleles is more likely that people would be different from one another, and that parents and children can be matched better.
There are a couple of problems with the HLA system, however. First, you need well preserved tissue or blood. That’s a little difficult sometimes. Second, HLA proteins are not always present in our cells. Third, a lot of mixtures of these genes go on when gametes are produced. Fourth, there are pretty common HLA alleles, and some extremely rare ones.
The Short Tandem Repeats
Human genome sequencing has revealed that the genome contains short sequences that are repeated many times in tandem. These are appropriately called Short Tandem Repeats (STR). For example, let’s consider the DNA sequence TCAT. Looking through the whole genome, there are different Short Tandem Repeats, and the repeat numbers are inherited. You might inherit one chromosome that has TCAT repeated five times, and the chromosome from the other parent might have TCAT repeated seven times.
You might ask how this block repeat happens. Molecular biologists, believe it or not, say that it is not clear how it happens. They have some ideas, though, but it is not clear. There are 10000 of STR’s scattered throughout the genome, but for DNA fingerprinting purposes, we use typically 13 of them.
These 13 repeated sequences are polymorphic. This means that there is more than one type of repeats. I might inherit five repeats of TCAT at a certain location, and seven from my other parent. If we were all the same for this repeat number, they wouldn’t do any good. These different numbers of repeats are what set us apart.
To analyze DNA this way, however, we need first to make a population survey. We need to know the frequencies of the alleles. For example, five TCAT are present 50% of the time in the population, and seven is present 50% also. If somebody comes across and has ten would be a totally different individual.
Supposing we are dealing with two of these 13 short tandem repeat chains, and that they have three alleles: A, B and C. Let’s say that the A allele is frequent in one person in a hundred. The B allele is one in five. The C allele is the more common, four in five. For the second short tandem repeat: A allele one in ten, B one in two, C two in five. A, B and C are just the number of repeats. A for example might be five, and B seven repeats.
So, let’s review:
Short Tandem Repeat 1:
A: one in a hundred
B: one in five
C: four in five
Short Tandem Repeat 2:
A: one in ten
B: one in two
C: two in five
Here is the key argument for doing DNA identification in this way. It comes from Mendel and probability. For a person to be carrying both the A and B alleles of STR number 1, the combined probability is the product of the two probabilities. The combined probability of A(1/100) and B(1/5) is:
The probability for STR number 2 A(one in ten) and B(one in two) is:
So, what is the probability of having both of them at once? Yes! It is the product of their probabilities:
We’re now getting a pretty low probability. One in ten thousand! This is the probability of carrying the four alleles: A and B of STR 1, A and B of STR 2. Think about it. We have 13 different systems for identifying people. If we’ve got these different alleles, the probability of two people having identical alleles is vanishingly low. It turns out that we’re all virtually unique in these sequences. That’s why DNA fingerprinting is so useful in identifying people.
Monday, March 1, 2010
Risks of Genetic Engineering
What are the risks of genetic engineering? The revolution that genetic engineering caused was profound. There was initially great concern about genetic engineering. The concerns centered on several aspects of this work. First, the bacteria used in these experiments were E. coli. This bacterium commonly lives on our intestines. People were worried about what will happen if this laboratory organism got out into our gut. Could the bacteria lead to cancer? This fear led almost to hysteria. Municipalities passed laws banning all genetic engineering work. A very famous scientist arrived to his laboratory one day to find the police out front, saying “you’ve broken our municipal ordinance against doing any gene swapping”. Doom scenarios were all over the place.
In 1975, a conference was held in California which brought together scientists, ethicists, physicians and lawyers to deal with this situation. This was a unique event in the history of science and government relations. The meeting was called by the scientists who were doing the work. They wanted some sort of feedback on what they were doing, because they were worried about the possible risks of genetic engineering.
At this meeting, after several days of heated discussions, they decided to do a moratorium on certain types of experiments. For example, until they knew what they were doing, they weren’t allowed to put cancer genes into bacteria to study them. They imposed extreme safety precautions on all of their types of experiments. Government agencies and institutional boards at research universities were set up to oversee this.
Scientists really asked for this oversight, which is very unusual, because scientists usually are of the type “just let us do our work and leave us alone, we would never harm you”. In this case, scientists were quite worried because this was so profound a change in biological manipulation.
In retrospect, these concerns were overblown, and no dangerous events have really occurred with genetic engineering. In fact, experiments that required severe precautions in 1975 are now done in high-school science labs. This doesn’t mean that we don’t need to constantly monitor this research. If we are dealing with harmful genes we must take extreme precautions.
In 1975, a conference was held in California which brought together scientists, ethicists, physicians and lawyers to deal with this situation. This was a unique event in the history of science and government relations. The meeting was called by the scientists who were doing the work. They wanted some sort of feedback on what they were doing, because they were worried about the possible risks of genetic engineering.
At this meeting, after several days of heated discussions, they decided to do a moratorium on certain types of experiments. For example, until they knew what they were doing, they weren’t allowed to put cancer genes into bacteria to study them. They imposed extreme safety precautions on all of their types of experiments. Government agencies and institutional boards at research universities were set up to oversee this.
Scientists really asked for this oversight, which is very unusual, because scientists usually are of the type “just let us do our work and leave us alone, we would never harm you”. In this case, scientists were quite worried because this was so profound a change in biological manipulation.
In retrospect, these concerns were overblown, and no dangerous events have really occurred with genetic engineering. In fact, experiments that required severe precautions in 1975 are now done in high-school science labs. This doesn’t mean that we don’t need to constantly monitor this research. If we are dealing with harmful genes we must take extreme precautions.
Good Things About Genetic Engineering
Here I want to talk about one of the good things about genetic engineering: using it to clean up the environment. I’ve already written about the benefits of genetic engineering in medicine and agriculture; let’s turn to the good things about genetic engineering regarding the environment. We can use bacteria as nature’s recyclers. Bacteria thrive on all sorts of nutrients, including things that we refer to as waste. There are species of bacteria that have the genetic capacity to produce enzymes that humans don’t. Composting uses bacteria to break down the carbon rich stores such as cellulose, which are the indigestible parts of wood chips, paper or straw. Also, they break down nitrogen rich sources, such as protein wastes and coffee grounds. When the bacteria work on these things, they produce four things: carbon dioxide, water, heat and humus.
Waste water treatment uses bacteria to act on human waste, paper products and household chemicals. The liquids and solids are treated differently. There is one group of bacteria that digest harmful substances in the solids of our wastes. Some of these bacteria, by the way, make a gas called methane as a byproduct, which is used for energy. Liquid wastes are digested by other bacteria. There is a whole series of bacteria that will digest different substances that are in things we call waste.
We’re still discovering more efficient and better ways to use bacteria for our purposes. This is called bioremediation.
Bacteria and plants have or can be given genes that remove pollutants. In addition to being nature’s recyclers, bacteria break down many human-made pollutants. How do we know this? We take soil with water, and we take that pollutant, oil for example. Then we look and see whether any of it gets broken down. We grow up the bacteria that thrive on the pollutant and use it.
In 1989, the oil tanker Exxon Valdez ran aground near the Alaskan shore, releasing 11 million gallons of crude oil over a thousand miles of shoreline. This was an environmental disaster of major proportions. Cleanup by physical methods was used first and the result was a dispersion of two thirds of the oil. Genetically engineered bacteria did the rest by bioremediation. Genetic strains of bacteria that can eat up oil were used. This process is ongoing.
The government of Kuwait is using bioremediation to try to clean up 150 million gallons of oil that was spilled probably deliberately by exploding oil wells during the Gulf War of 1991. This is probably the largest single remediation project in the world, and it is going on as I write. This is maybe one of the most useful of the good things about genetic engineering.
Good Things About Genetic Engineering? Environmental Cleanup
There is a type of bacteria called extremophiles. They have many genes that are useful in bioremediation. Extremophiles are bacteria that love the extremes of nature. They are kind of the ultimate athletes of the biological world. They can live in very hot places or icy places like Antarctica, or deep in the ocean, or very salty environments like the Dead Sea. These organisms form a separate group from bacteria called the archaea. They are called archaea because they resemble the organisms that are believed were the first living cells.
The archaea genomes have been sequenced and half of the genes of the archaea do not resemble anything in any types of bacteria or eukaryotes. Some of them have genes that use carbon dioxide, just like plants do, not to make sugars but to make methane gas. Archaea are by far the major producers of this gas.
The granddaddy of all archaea is called Deinococcus radiodurans. This organism lives in probably the most dangerous environment on Earth: ones with extremely high levels of radiation. Normally, radiation kills cells by damaging DNA. When DNA in any cell is damaged by radiation, we can repair it thanks to a system that we have. Large amounts of radiation, however, overwhelm that, and you get permanent mutations and cancers as a result.
Deinococcus radiodurans gets around this by having the most efficient and sensitive radiation repair system in nature. It is a phenomenally good system. This wonderful organism is responsible by one of the good things about genetic engineering. Genes from other extremophiles are being engineered into Deinococcus radiodurans. People call this new organism Conan the Bacterium. It is used to clean up the most toxic sites we know of. For example, in America there are sites extremely contaminated with extremely bad stuff. These Deinococcus radiodurans are being used there.
Plants can be genetically engineered for environmental cleanup. For instance, bacterial genes that allow environmental cleanup can be put into transgenic plants to break down oil. There are plants that would convert solid mercury into harmless substances. They might ask why use plants when microbes are available. The issue is that you want to get the microbe out of the soil when you don’t need it anymore. You don’t want extra microbes. Getting bacteria out of the soil is quite difficult. Plants are easy to take out. You plant it, it does its thing, and you take it out. This might be a better way of doing bioremediation in some cases.
Waste water treatment uses bacteria to act on human waste, paper products and household chemicals. The liquids and solids are treated differently. There is one group of bacteria that digest harmful substances in the solids of our wastes. Some of these bacteria, by the way, make a gas called methane as a byproduct, which is used for energy. Liquid wastes are digested by other bacteria. There is a whole series of bacteria that will digest different substances that are in things we call waste.
We’re still discovering more efficient and better ways to use bacteria for our purposes. This is called bioremediation.
Bacteria and plants have or can be given genes that remove pollutants. In addition to being nature’s recyclers, bacteria break down many human-made pollutants. How do we know this? We take soil with water, and we take that pollutant, oil for example. Then we look and see whether any of it gets broken down. We grow up the bacteria that thrive on the pollutant and use it.
In 1989, the oil tanker Exxon Valdez ran aground near the Alaskan shore, releasing 11 million gallons of crude oil over a thousand miles of shoreline. This was an environmental disaster of major proportions. Cleanup by physical methods was used first and the result was a dispersion of two thirds of the oil. Genetically engineered bacteria did the rest by bioremediation. Genetic strains of bacteria that can eat up oil were used. This process is ongoing.
The government of Kuwait is using bioremediation to try to clean up 150 million gallons of oil that was spilled probably deliberately by exploding oil wells during the Gulf War of 1991. This is probably the largest single remediation project in the world, and it is going on as I write. This is maybe one of the most useful of the good things about genetic engineering.
Good Things About Genetic Engineering? Environmental Cleanup
There is a type of bacteria called extremophiles. They have many genes that are useful in bioremediation. Extremophiles are bacteria that love the extremes of nature. They are kind of the ultimate athletes of the biological world. They can live in very hot places or icy places like Antarctica, or deep in the ocean, or very salty environments like the Dead Sea. These organisms form a separate group from bacteria called the archaea. They are called archaea because they resemble the organisms that are believed were the first living cells.
The archaea genomes have been sequenced and half of the genes of the archaea do not resemble anything in any types of bacteria or eukaryotes. Some of them have genes that use carbon dioxide, just like plants do, not to make sugars but to make methane gas. Archaea are by far the major producers of this gas.
The granddaddy of all archaea is called Deinococcus radiodurans. This organism lives in probably the most dangerous environment on Earth: ones with extremely high levels of radiation. Normally, radiation kills cells by damaging DNA. When DNA in any cell is damaged by radiation, we can repair it thanks to a system that we have. Large amounts of radiation, however, overwhelm that, and you get permanent mutations and cancers as a result.
Deinococcus radiodurans gets around this by having the most efficient and sensitive radiation repair system in nature. It is a phenomenally good system. This wonderful organism is responsible by one of the good things about genetic engineering. Genes from other extremophiles are being engineered into Deinococcus radiodurans. People call this new organism Conan the Bacterium. It is used to clean up the most toxic sites we know of. For example, in America there are sites extremely contaminated with extremely bad stuff. These Deinococcus radiodurans are being used there.
Plants can be genetically engineered for environmental cleanup. For instance, bacterial genes that allow environmental cleanup can be put into transgenic plants to break down oil. There are plants that would convert solid mercury into harmless substances. They might ask why use plants when microbes are available. The issue is that you want to get the microbe out of the soil when you don’t need it anymore. You don’t want extra microbes. Getting bacteria out of the soil is quite difficult. Plants are easy to take out. You plant it, it does its thing, and you take it out. This might be a better way of doing bioremediation in some cases.
Stem Cell Research
Stem cell research is in our news all the time, both from a scientific point of view and a political point of view. Today we’re on the threshold of stealing a power from the gods, the power to regenerate human organs and make life much longer. There are some people who fear retribution from the gods, but I know we’re going to do this anyway. Our scientists, no matter what the political climate is, are going to learn how to use stem cells to regenerate organs.
What are Stem Cells?
Stem cells are unspecialized cells in the body that constantly divide to form a pool of cells that can then specialize when they are needed. The ultimate stem cells are embryonic stem cells. They are totipotent. They can become any cell in the organism. In laboratory experiments on animals, these embryonic stem cells can be induced to form many different cell types. In animals, these cell types coming from embryonic stem cells have cured brain damage, heart damage, muscle damage, etc. This has generated great excitement for stem cell research.
The proposal is to use laboratory grown stem cells as a supply. You don’t need a lot of embryos to do this. The problem is that if I get some stem cells from someone else, they’re not mine. Those cells going into my heart would do the work, but then my immune system would ultimately reject them.
What is the advantage of stem cell research?
There is a need for new cells in medicine to replace cells that are damaged. For example, in a heart attack, the heart muscle is damaged, and it is usually permanent damage. How are you going to replace that tissue? In the brain, Parkinson’s disease and others result from a lack of functional cells. Diabetes, specially type 1, the pancreas is damaged. Let’s get new cells to replace these!
Stem cell transplants are already performed every day. Bone marrow gets damaged when cancer is treated with radiation therapy and chemotherapy. All the cells, including the stem cells inside the bone marrow, are damaged. A person who is treated with radiation and chemotherapy for cancer is going to be severely anemic and immune-compromised; because their immune system would not be working (white blood cells would not be produced in sufficient numbers).
What are Stem Cells?
Stem cells are unspecialized cells in the body that constantly divide to form a pool of cells that can then specialize when they are needed. The ultimate stem cells are embryonic stem cells. They are totipotent. They can become any cell in the organism. In laboratory experiments on animals, these embryonic stem cells can be induced to form many different cell types. In animals, these cell types coming from embryonic stem cells have cured brain damage, heart damage, muscle damage, etc. This has generated great excitement for stem cell research.
The proposal is to use laboratory grown stem cells as a supply. You don’t need a lot of embryos to do this. The problem is that if I get some stem cells from someone else, they’re not mine. Those cells going into my heart would do the work, but then my immune system would ultimately reject them.
What is the advantage of stem cell research?
There is a need for new cells in medicine to replace cells that are damaged. For example, in a heart attack, the heart muscle is damaged, and it is usually permanent damage. How are you going to replace that tissue? In the brain, Parkinson’s disease and others result from a lack of functional cells. Diabetes, specially type 1, the pancreas is damaged. Let’s get new cells to replace these!
Stem cell transplants are already performed every day. Bone marrow gets damaged when cancer is treated with radiation therapy and chemotherapy. All the cells, including the stem cells inside the bone marrow, are damaged. A person who is treated with radiation and chemotherapy for cancer is going to be severely anemic and immune-compromised; because their immune system would not be working (white blood cells would not be produced in sufficient numbers).
Cancer Prevention
Let’s talk about cancer prevention. What can we do to prevent it? Cancer is the second leading cause of death in the United States, and the most feared diagnosis. Although heart disease is the number one killer of Americans, the diagnosis of cancer is the most terrifying. Clearly we have much to do in the prevention of cancer. Poor diet is estimated to account for 30% to 35% of the cancers. Therefore, we can do something to modify our risk. Please keep in mind that modification of risk does not preclude the need for early detection and diagnosis. Although you might do everything possible in terms of diet and exercise, make sure you keep up with diagnostic testing.
Outside of diet, there are other lifestyle risk factors: tobacco use, alcohol consumption and lack of exercise. These can increase the overall risk of almost all cancers.
Here I want to talk about the dietary strategies and lifestyle modifications needed to reduce cancer risk.
Both tobacco and alcohol initiate and promote cancer development. Not only they cause cell damage, they also promote cancer development.
The American Cancer Society suggests that 1 million skin cancers could be prevented by eliminating sun exposure. This is a double edged sword. We know that the sun is a great source of vitamin D. By eliminating sun exposure, you can also eliminate one of your major sources of vitamin D. Sun screen can be very effective for preventing skin cancer, but it must be applied in an appropriate way. The higher the Sun Protection Factor (SPF), the better.
Exposure to UV light in tanning salons can be just as dangerous as exposure to the sun itself.
Some of the most exciting things in terms of cancer development is that we now know that certain viruses have been implicated in cervical cancer and possibly others as well. New vaccines can be given to prevent certain forms but not all of cervical cancer.
The current thinking is that nutrition can either act as a cancer promoter or a cancer-cell killer. According to the American Cancer society, diet and weight management can aid in the prevention of cancer. If you’re struggling with weight management and exercise, you might want to think about this as your deposit in the cancer prevention account.
There appears to be a dose-related response to exercise. That means that 30 minutes of exercise is good, but an hour would be better. Human bodies evolved to move. Apparently, in this case, what is happening is that individuals who do not exercise become resistant to insulin. They make of it, and the more you make, more you promote cancer development.
Simple Recommendations
What do you think of a plant-based diet? The more of your plate is occupied by vegetables, the better. Think about having a meat-less Monday, were your main dish might be vegetarian.
A recent study that included more than half a million subjects (this is a lot!!) suggest that those who consume the highest amount of red meat have a higher mortality rate. This study is known as the NIH-AARP Diet and Health Study. Mortality rates from both heart disease and cancer were increased with increasing red meat consumption.
What are some big recommendations from this study? Reduce the meat and avoid grilling. Grilling can increase the charring of that meat. It is the charred meat that can increase the risk of cancer.
Well, suppose you’re invited over somebody’s house and they are not really great with their grilling skills and you’ve got everything that’s significantly blackened. Trim off as much of that as you can and maybe flavor it up with a bit of barbecue sauce.
Regarding alcohol use in cancer prevention, the best approach is no alcohol. Keep in mind that alcohol minimally is going to serve as an initiating event. If you do drink alcohol, the recommendation is to limit your intake to one drink per day for women and two for men.
Avoid cured meats. These are processed meats, such as bacon, ham and hot dogs. Individuals are trying to get away from beef and pork, we now have cured turkey products. We have now turkey hot dogs and everyone believes that’s better for them. The problem is the curing of the meat. Cancer-causing compounds are formed when meats are cured.
Well, here I ended talking more about what we should avoid to prevent cancer. In my next post I’ll talk about a healthy diet and lifestyle that would help in cancer prevention.
Outside of diet, there are other lifestyle risk factors: tobacco use, alcohol consumption and lack of exercise. These can increase the overall risk of almost all cancers.
Here I want to talk about the dietary strategies and lifestyle modifications needed to reduce cancer risk.
Both tobacco and alcohol initiate and promote cancer development. Not only they cause cell damage, they also promote cancer development.
The American Cancer Society suggests that 1 million skin cancers could be prevented by eliminating sun exposure. This is a double edged sword. We know that the sun is a great source of vitamin D. By eliminating sun exposure, you can also eliminate one of your major sources of vitamin D. Sun screen can be very effective for preventing skin cancer, but it must be applied in an appropriate way. The higher the Sun Protection Factor (SPF), the better.
Exposure to UV light in tanning salons can be just as dangerous as exposure to the sun itself.
Some of the most exciting things in terms of cancer development is that we now know that certain viruses have been implicated in cervical cancer and possibly others as well. New vaccines can be given to prevent certain forms but not all of cervical cancer.
The current thinking is that nutrition can either act as a cancer promoter or a cancer-cell killer. According to the American Cancer society, diet and weight management can aid in the prevention of cancer. If you’re struggling with weight management and exercise, you might want to think about this as your deposit in the cancer prevention account.
There appears to be a dose-related response to exercise. That means that 30 minutes of exercise is good, but an hour would be better. Human bodies evolved to move. Apparently, in this case, what is happening is that individuals who do not exercise become resistant to insulin. They make of it, and the more you make, more you promote cancer development.
Simple Recommendations
What do you think of a plant-based diet? The more of your plate is occupied by vegetables, the better. Think about having a meat-less Monday, were your main dish might be vegetarian.
A recent study that included more than half a million subjects (this is a lot!!) suggest that those who consume the highest amount of red meat have a higher mortality rate. This study is known as the NIH-AARP Diet and Health Study. Mortality rates from both heart disease and cancer were increased with increasing red meat consumption.
What are some big recommendations from this study? Reduce the meat and avoid grilling. Grilling can increase the charring of that meat. It is the charred meat that can increase the risk of cancer.
Well, suppose you’re invited over somebody’s house and they are not really great with their grilling skills and you’ve got everything that’s significantly blackened. Trim off as much of that as you can and maybe flavor it up with a bit of barbecue sauce.
Regarding alcohol use in cancer prevention, the best approach is no alcohol. Keep in mind that alcohol minimally is going to serve as an initiating event. If you do drink alcohol, the recommendation is to limit your intake to one drink per day for women and two for men.
Avoid cured meats. These are processed meats, such as bacon, ham and hot dogs. Individuals are trying to get away from beef and pork, we now have cured turkey products. We have now turkey hot dogs and everyone believes that’s better for them. The problem is the curing of the meat. Cancer-causing compounds are formed when meats are cured.
Well, here I ended talking more about what we should avoid to prevent cancer. In my next post I’ll talk about a healthy diet and lifestyle that would help in cancer prevention.
Genetic Engineering
Genetic Engineering is the manipulation of microbes, plants and animals to make products that are useful to people. As such, this technology is not new. It began a long time ago. I would say that biotechnology began with agriculture.
What is Genetic Engineering?
Estimates are that agriculture probably began about 10000 years ago, in what is now the region near Iraq. We have evidence that Sumerians living there at the time learned that barley plants growing around their homes made seeds that could be used to make bear and bread. They started growing these seeds near their settlements. They would use some of the seeds to make bear and bread, and then they would grow the rest of the seeds nearby. This was the first biotechnology.
A History of Genetic Engineering
Werner Arber was born in 1929. As a graduate student at the University of Geneva in the 1950’s, he studied with a physics professor who converted from doing pure physics to biophysics. Arber’s PhD thesis was on the phenomenon of bacteriophages restriction. He didn’t even suspect that his research would begin a revolution.
In 1973, scientists had taken two chromosomes, cut them open, put them back together, and showed that they were functional in a cell. They had created genetically functional recombinant DNA. It was a revolutionary discovery.
Review the timeline of genetic engineering.
Benefits of Genetic Engineering
The first major product of biotechnology was human insulin. This type of insulin is now used to treat type 1 diabetics. Another example is the blood-clotting protein that is missing in hemophilia.
There is a protein called Erythropoietin (EPO). EPO is a hormone-like substance made by the kidneys. The gene coding for EPO was isolated, EPO was made by recombinant DNA technology, and this is now widely used for people who are undergoing kidney dialysis and also people who are being treated with cancer chemotherapy.
There are a significant number of humans that lack adequate amounts of growth hormone. These people are very short in stature. The growth hormone is a protein. So, again, we got to get it through recombinant DNA technology.
We can use biotechnology to have a plant make a vaccine. You could become immune to a disease simply by eating a fruit. Pretty nice, eh?
These are just a few benefits of this new technology.
Genetic Engineering in Agriculture
According to UN estimates, human population will level off at about 10 billion people. Can biotechnology help solve this issue? A real problem in agriculture that existed for millennia is that most plants cannot grow in salty soils. Salt-tolerant transgenic plants may make deserts bloom again.
Other applications of biotechnology in agricultura are:
Plants That Make Their Own Insecticide
Plants Resistant to Herbicides
Nutritionally Rich Crops
Problems with Genetic Engineering
The first supposed problem is that genetic manipulation is an unnatural manipulation of nature. This is what philosophers call the “yuck factor”. According to this argument, eating food from a plant that has genes from bacteria is just “going too far”. There is no real response to this emotional argument.
The second of the supposed problems is that genetically modified foods might be unsafe to eat. It turns out that most genetically modified plants grown today are not altered in the food part of the plant. We’ve got to be careful with allergies, however.
The third of the risks is that genetically modified plants may be dangerous to the environment. This is maybe a real risk, but not a really serious one.
What is Genetic Engineering?
Estimates are that agriculture probably began about 10000 years ago, in what is now the region near Iraq. We have evidence that Sumerians living there at the time learned that barley plants growing around their homes made seeds that could be used to make bear and bread. They started growing these seeds near their settlements. They would use some of the seeds to make bear and bread, and then they would grow the rest of the seeds nearby. This was the first biotechnology.
A History of Genetic Engineering
Werner Arber was born in 1929. As a graduate student at the University of Geneva in the 1950’s, he studied with a physics professor who converted from doing pure physics to biophysics. Arber’s PhD thesis was on the phenomenon of bacteriophages restriction. He didn’t even suspect that his research would begin a revolution.
In 1973, scientists had taken two chromosomes, cut them open, put them back together, and showed that they were functional in a cell. They had created genetically functional recombinant DNA. It was a revolutionary discovery.
Review the timeline of genetic engineering.
Benefits of Genetic Engineering
The first major product of biotechnology was human insulin. This type of insulin is now used to treat type 1 diabetics. Another example is the blood-clotting protein that is missing in hemophilia.
There is a protein called Erythropoietin (EPO). EPO is a hormone-like substance made by the kidneys. The gene coding for EPO was isolated, EPO was made by recombinant DNA technology, and this is now widely used for people who are undergoing kidney dialysis and also people who are being treated with cancer chemotherapy.
There are a significant number of humans that lack adequate amounts of growth hormone. These people are very short in stature. The growth hormone is a protein. So, again, we got to get it through recombinant DNA technology.
We can use biotechnology to have a plant make a vaccine. You could become immune to a disease simply by eating a fruit. Pretty nice, eh?
These are just a few benefits of this new technology.
Genetic Engineering in Agriculture
According to UN estimates, human population will level off at about 10 billion people. Can biotechnology help solve this issue? A real problem in agriculture that existed for millennia is that most plants cannot grow in salty soils. Salt-tolerant transgenic plants may make deserts bloom again.
Other applications of biotechnology in agricultura are:
Plants That Make Their Own Insecticide
Plants Resistant to Herbicides
Nutritionally Rich Crops
Problems with Genetic Engineering
The first supposed problem is that genetic manipulation is an unnatural manipulation of nature. This is what philosophers call the “yuck factor”. According to this argument, eating food from a plant that has genes from bacteria is just “going too far”. There is no real response to this emotional argument.
The second of the supposed problems is that genetically modified foods might be unsafe to eat. It turns out that most genetically modified plants grown today are not altered in the food part of the plant. We’ve got to be careful with allergies, however.
The third of the risks is that genetically modified plants may be dangerous to the environment. This is maybe a real risk, but not a really serious one.
Cell culture H1N1 vacc could be ready in 3 months
industry response to the h1n1 pandemic suggests that cell culture vaccine production is about to come of age with two firms that use the technique, novartis and baxter, claiming it will cut development and manufacturing timelines by months.
Margaret Chan officially declared the pandemic explaining that H1N1 infections worldwide can no longer be traced and that “further spread is considered inevitable.” She asked drugmakers to begin preparing for large-scale H1N1 vaccine production when manufacture of seasonal stocks is completed, prompting a flurry of industry updates from vaccine producers.
Baxter and Novartis aim for early availability
The most eye-catching of these responses came from US drugmaker Baxter which announced it has completed testing of its Celvapan H1N1 vaccine and is “now in full-scale production,” and is working to deliver it as early as next month. Traditionally, seasonal influenza vaccines are mass produced using the albumin found in fertilised hens eggs as a growth media.
Swiss drug major Novartis made similar claims for its cell culture developed vaccine, although it was more measured about its timelines.
Novartis said it completed making the first batch of a H1N1 vaccine weeks ahead of expectations, explaining that its culture system allows production to begin “without the need to adapt the virus strain to grow in eggs, as with traditional…technologies.”
The firm, which claims to have been asked to supply vaccine ingredients by more than 30 countries, said it will begin trials of its product next month and expects to obtain regulatory approval for the vaccine in the autumn.
In a follow up statement reported by London’s Financial Times yesterday, Novartis said that it “will not give free vaccines against H1N1 flu to poor countries, though it will consider discounts.”
GSK, Sanofi and CSL
The response of companies that use egg-based production methods was more uniform, with almost all saying that large-scale manufacture will begin by September at the earliest.
Initial media reports suggested that Australia’s CSL will finish making the first batch of its vaccine ahead of producers like GlaxoSmithKline (GSK) and Sanofi Aventis, although this was later denied by company spokesperson Rachel Davis.
Margaret Chan officially declared the pandemic explaining that H1N1 infections worldwide can no longer be traced and that “further spread is considered inevitable.” She asked drugmakers to begin preparing for large-scale H1N1 vaccine production when manufacture of seasonal stocks is completed, prompting a flurry of industry updates from vaccine producers.
Baxter and Novartis aim for early availability
The most eye-catching of these responses came from US drugmaker Baxter which announced it has completed testing of its Celvapan H1N1 vaccine and is “now in full-scale production,” and is working to deliver it as early as next month. Traditionally, seasonal influenza vaccines are mass produced using the albumin found in fertilised hens eggs as a growth media.
Swiss drug major Novartis made similar claims for its cell culture developed vaccine, although it was more measured about its timelines.
Novartis said it completed making the first batch of a H1N1 vaccine weeks ahead of expectations, explaining that its culture system allows production to begin “without the need to adapt the virus strain to grow in eggs, as with traditional…technologies.”
The firm, which claims to have been asked to supply vaccine ingredients by more than 30 countries, said it will begin trials of its product next month and expects to obtain regulatory approval for the vaccine in the autumn.
In a follow up statement reported by London’s Financial Times yesterday, Novartis said that it “will not give free vaccines against H1N1 flu to poor countries, though it will consider discounts.”
GSK, Sanofi and CSL
The response of companies that use egg-based production methods was more uniform, with almost all saying that large-scale manufacture will begin by September at the earliest.
Initial media reports suggested that Australia’s CSL will finish making the first batch of its vaccine ahead of producers like GlaxoSmithKline (GSK) and Sanofi Aventis, although this was later denied by company spokesperson Rachel Davis.
New Microarray Technology
Moxtek, a nano-photonics company, today announced that it has reached a collaboration agreement with Philips Research to develop a new wire grid microarray chip (WGM) that has been designed to offer ultra-high surface specificity and excellent suppression of background signals. The WGM is based on a wire grid pattern on a glass substrate.
The WGM technology provides the potential for rapid quantitative detection with improved accuracy, of biomolecules such as proteins and nucleic acids. In addition, the technology promises to significantly simplify the work flow and improve the reproducibility for such tests by removing the washing step and performing hybridization and detection in parallel. These strengths match with the needs for advanced microarray technology in life sciences research. Rapid molecular detection for life sciences research is a fast-growing market, and could revolutionize healthcare research.
The WGM is based on illumination of a grid of metal nanowires with polarized excitation light and detecting the fluorescence generated by fluorescently labeled target molecules bound to capture probes on the substrate between the metal nanowires. The detection volume is limited to ~20 nm above the surface, and can be controlled via the dimensions of the nanowires and the excitation wavelength. The surface specific detection of the WGM provides a significant reduction in microarray workflow by making redundant the chip washing step; moreover, it has been shown to allow monitoring the binding of bio-molecules to the substrate in real-time.
Control of the polarization state enables using the wire grid microarray concept for both highly surface specific measurements and “conventional” measurements where the measurement volume is determined by the optical set-up rather than the geometry of the wire grid. This versatile technique has been designed to be compatible with commercial optical microarray readers currently available on the market.
The WGM technology provides the potential for rapid quantitative detection with improved accuracy, of biomolecules such as proteins and nucleic acids. In addition, the technology promises to significantly simplify the work flow and improve the reproducibility for such tests by removing the washing step and performing hybridization and detection in parallel. These strengths match with the needs for advanced microarray technology in life sciences research. Rapid molecular detection for life sciences research is a fast-growing market, and could revolutionize healthcare research.
The WGM is based on illumination of a grid of metal nanowires with polarized excitation light and detecting the fluorescence generated by fluorescently labeled target molecules bound to capture probes on the substrate between the metal nanowires. The detection volume is limited to ~20 nm above the surface, and can be controlled via the dimensions of the nanowires and the excitation wavelength. The surface specific detection of the WGM provides a significant reduction in microarray workflow by making redundant the chip washing step; moreover, it has been shown to allow monitoring the binding of bio-molecules to the substrate in real-time.
Control of the polarization state enables using the wire grid microarray concept for both highly surface specific measurements and “conventional” measurements where the measurement volume is determined by the optical set-up rather than the geometry of the wire grid. This versatile technique has been designed to be compatible with commercial optical microarray readers currently available on the market.
The good news in our DNA: Defects you can fix with vitamins and minerals
As the cost of sequencing a single human genome drops rapidly, with one company predicting a price of $100 per person in five years, soon the only reason not to look at your "personal genome" will be fear of what bad news lies in your genes.
University of California, Berkeley, scientists, however, have found a welcome reason to delve into your genetic heritage: to find the slight genetic flaws that can be fixed with remedies as simple as vitamin or mineral supplements.
"There are over 600 human enzymes that use vitamins or minerals as cofactors, and this study reports just what we found by studying one of them," Rine said. "What this means is that, even if the odds of an individual having a defect in one gene is low, with 600 genes, we are all likely to have some mutations that limit one or more of our enzymes."
The subtle effects of variation in enzyme activity may well account for conflicting results of some clinical trials, including the confusing data on the effect of vitamin supplements, he noted. In the future, the enzyme profile of research subjects will have to be taken into account in analyzing the outcome of clinical trials.
If one considers not just vitamin-dependent enzymes but all the 30,000 human proteins in the genome, "every individual would harbor approximately 250 deleterious substitutions considering only the low-frequency variants. These numbers suggest that the aggregate incidence of low-frequency variants could have a significant physiological impact," the researchers wrote in their paper.
University of California, Berkeley, scientists, however, have found a welcome reason to delve into your genetic heritage: to find the slight genetic flaws that can be fixed with remedies as simple as vitamin or mineral supplements.
"There are over 600 human enzymes that use vitamins or minerals as cofactors, and this study reports just what we found by studying one of them," Rine said. "What this means is that, even if the odds of an individual having a defect in one gene is low, with 600 genes, we are all likely to have some mutations that limit one or more of our enzymes."
The subtle effects of variation in enzyme activity may well account for conflicting results of some clinical trials, including the confusing data on the effect of vitamin supplements, he noted. In the future, the enzyme profile of research subjects will have to be taken into account in analyzing the outcome of clinical trials.
If one considers not just vitamin-dependent enzymes but all the 30,000 human proteins in the genome, "every individual would harbor approximately 250 deleterious substitutions considering only the low-frequency variants. These numbers suggest that the aggregate incidence of low-frequency variants could have a significant physiological impact," the researchers wrote in their paper.
Invitrogen and Applied Biosystems to combine
Invitrogen Corporation and Applera Corporation today announced that their Boards of Directors have approved a definitive merger agreement, under which Invitrogen will acquire all of the outstanding shares of Applera's Applied Biosystems Group a cash and stock transaction valued at $6.7 billion.
This strategic combination will create a global leader in biotechnology reagents and systems generating approximately $3.5 billion in combined sales, with significant commercial, operational and technical scale, uniquely positioned to accelerate and drive new discoveries and commercial applications. The combined company will have a major presence in key growth markets and exceptional technical capabilities in the areas of genetic analysis, proteomics, cell biology and cell systems. Following the close of the transaction, the combined organization will be named Applied Biosystems, Inc. and will have its corporate headquarters in Carlsbad, California.
Under the terms of the merger agreement, Applera-Applied Biosystems shareholders will receive $38.00 for each share of Applera-Applied Biosystems stock they own in the form of Invitrogen common stock and cash. The expected split between cash and stock is 45% and 55%, respectively. Applera-Applied Biosystems shareholders will receive a value of $38.00 a share if the 20 day volume-weighted average price of Invitrogen common stock is in the range of $43.69 - $46.00 three business days prior to the close of the transaction. The total value per share will differ if Invitrogen's 20 day volume-weighted average price is above or below that range, measured shortly prior to the close of the transaction. The consideration represents a premium of 17% to Applied Biosystems's closing price on June 11, 2008, or 12% to Applied Biosystems's average closing price in the last 30 trading days. Applera-Applied Biosystems shareholders also will have the option to request all cash or all stock, subject to possible proration. Upon completion of the transaction, Invitrogen shareholders will own the majority of the company.
This strategic combination will create a global leader in biotechnology reagents and systems generating approximately $3.5 billion in combined sales, with significant commercial, operational and technical scale, uniquely positioned to accelerate and drive new discoveries and commercial applications. The combined company will have a major presence in key growth markets and exceptional technical capabilities in the areas of genetic analysis, proteomics, cell biology and cell systems. Following the close of the transaction, the combined organization will be named Applied Biosystems, Inc. and will have its corporate headquarters in Carlsbad, California.
Under the terms of the merger agreement, Applera-Applied Biosystems shareholders will receive $38.00 for each share of Applera-Applied Biosystems stock they own in the form of Invitrogen common stock and cash. The expected split between cash and stock is 45% and 55%, respectively. Applera-Applied Biosystems shareholders will receive a value of $38.00 a share if the 20 day volume-weighted average price of Invitrogen common stock is in the range of $43.69 - $46.00 three business days prior to the close of the transaction. The total value per share will differ if Invitrogen's 20 day volume-weighted average price is above or below that range, measured shortly prior to the close of the transaction. The consideration represents a premium of 17% to Applied Biosystems's closing price on June 11, 2008, or 12% to Applied Biosystems's average closing price in the last 30 trading days. Applera-Applied Biosystems shareholders also will have the option to request all cash or all stock, subject to possible proration. Upon completion of the transaction, Invitrogen shareholders will own the majority of the company.
DNA is clearly in the public consciousness
It is true that the DNA has become vernacular now, blogging previously on the Genome entering the drawing rooms in Dawn of the GATTACA era! found another cute, small and interesting article which relates to this interesting fact on how common a word is the "DNA" now When you care enough to send the very best DNA. After reading it i felt in days to come, well we might have MATTEL come out with a "Francis Crick DNA code-breaker toy" fighting and saving the world and a "Craig Venter" toy challenging him...
GNA-glycerol nucleic acid—a synthetic analog of DNA
Biodesign Institute colleague John Chaput is working to give researchers brand new materials to aid their designs. In an article recently published in the Journal of the American Chemical Society, Chaput and his research team have made the first self-assembled nanostructures composed entirely of glycerol nucleic acid (GNA)—a synthetic analog of DNA.
“Everyone in DNA nanotechnology is essentially limited by what they can buy off the shelf,” said Chaput, who is also an ASU assistant professor in the Department of Chemistry and Biochemistry. “We wanted to build synthetic molecules that assembled like DNA, but had additional properties not found in natural DNA.”
The DNA helix is made up of just three simple parts: a sugar and a phosphate molecule that form the backbone of the DNA ladder, and one of four nitrogenous bases that make up the rungs. The nitrogenous base pairing rules in the DNA chemical alphabet fold DNA into a variety of useful shapes for nanotechnology, given that "A" can only form a zipper-like chemical bond with "T" and "G" only pair with "C."
In the case of GNA, the sugar is the only difference with DNA. The five carbon sugar commonly found in DNA, called deoxyribose, is substituted by glycerol, which contains just three carbon atoms.
In nature, many molecules important to life like DNA and proteins have evolved to exist only as right-handed. The GNA structures, unlike DNA, turned out to be ‘enantiomeric’ molecules, which in chemical terms means both left and right-handed.
“Making GNA is not tricky, it’s just three steps, and with three carbon atoms, only one stereo center,” said Chaput. “It allows us to make these right and left-handed biomolecules. People have actually made left-handed DNA, but it is a synthetic nightmare. To use it for DNA nanotechnology could never work. It’s too high of a cost to make, so one could never get enough material.”
Sunday, February 28, 2010
PCR (Polymerase Chain Reaction)
IT is a technique in which cycles of denaturation, annealing with primer, and extension with DNA polymerase, are used to amplify the number of copies of a target DNA sequence by more than 100 times in a few hours. American molecular biologist Kary Mullis developed the techniques of PCR in the 1970s. For his ingenious invention, he was awarded the 1993 Nobel Prize in physiology or medicine.
PCR amplification of DNA is like any DNA replication by DNA polymerase in vivo. (in lving cells) The difference is that PCR produces DNA in a test tube. For a PCR reaction to proceed, four components are necessary: template, primer, deoxyribonecleotides (adenine, thymine, cytosine, guanine) and DNA polymerase. In addition, part of the sequence of the targeted DNA has to be known in order to design the according primers. In the first step, the targeted double stranded DNA is heated to over 194°F (90°C) for denaturation. During this process, two strands of the targeted DNA are separated from each other. Each strand is capable of being a template. The second step is carried out around 122° (50°C). At this lowered temperature, the two primers anneal to their complementary sequence on each template. The DNA polymerase then extends the primer using the provided NUCLEOTIDES. As a result, at the end of each cycle, the numbers of DNA molecules double.
PCR was initially carried out manually in incubators of different temperatures for each step until the extraction of DNA polymerase from thermophilic bacteria. The bacterium Thermus aquaticus was found in Yellow Stone National Park. This bacterium lives in the hot springs at 203°F (95°C). The DNA polymerase from T. aquaticus keeps its activity at above 95°C for many hours. Several additional heat-resistant DNA polymerases have also now been identified.
PCR amplification of DNA is like any DNA replication by DNA polymerase in vivo. (in lving cells) The difference is that PCR produces DNA in a test tube. For a PCR reaction to proceed, four components are necessary: template, primer, deoxyribonecleotides (adenine, thymine, cytosine, guanine) and DNA polymerase. In addition, part of the sequence of the targeted DNA has to be known in order to design the according primers. In the first step, the targeted double stranded DNA is heated to over 194°F (90°C) for denaturation. During this process, two strands of the targeted DNA are separated from each other. Each strand is capable of being a template. The second step is carried out around 122° (50°C). At this lowered temperature, the two primers anneal to their complementary sequence on each template. The DNA polymerase then extends the primer using the provided NUCLEOTIDES. As a result, at the end of each cycle, the numbers of DNA molecules double.
PCR was initially carried out manually in incubators of different temperatures for each step until the extraction of DNA polymerase from thermophilic bacteria. The bacterium Thermus aquaticus was found in Yellow Stone National Park. This bacterium lives in the hot springs at 203°F (95°C). The DNA polymerase from T. aquaticus keeps its activity at above 95°C for many hours. Several additional heat-resistant DNA polymerases have also now been identified.
DNA Fingerprinting
Genetic, genomic, or DNA fingerprinting is the term applied to a range of techniques that are used to show similarities and dissimilarities between the DNA present in different individuals.
Genetic fingerprinting is an important tool in the arsenal of forensic investigators. Genetic fingerprinting allows for positive identification, not only of body remains, but also of suspects in custody. Genetic fingerprinting can also link suspects to physical evidence.
Sir Alec Jeffreys at the University of Leicester developed DNA fingerprinting in the mid 1980s. The sequence of NUCLEOTIDES in DNA is similar to a fingerprint, in that it is unique to each person. DNA fingerprinting is used for identifying people, studying populations, and forensic investigations.
Genetic fingerprinting is an important tool in the arsenal of forensic investigators. Genetic fingerprinting allows for positive identification, not only of body remains, but also of suspects in custody. Genetic fingerprinting can also link suspects to physical evidence.
Sir Alec Jeffreys at the University of Leicester developed DNA fingerprinting in the mid 1980s. The sequence of NUCLEOTIDES in DNA is similar to a fingerprint, in that it is unique to each person. DNA fingerprinting is used for identifying people, studying populations, and forensic investigations.
Recombinant DNA
Deoxyribonucleic acid (DNA) is the information blueprint that exists in most living organisms. Some viruses instead contain ribonucleic acid (RNA). Even these viruses require the production of DNA at some stage of their replication.
DNA from different organisms of the same species combines together naturally to yield an organism that has traits from both parent organisms. There is also evidence accumulating that DNA transfer between different species may be a natural process. However, much interspecies mixing of DNA is the result of deliberate experimental manipulations.
A crucial process of these manipulations is the preparation of recombinant DNA. Recombinant DNA is DNA from different organisms that have been chemically bonded together to form a single DNA. The recombinant DNA can be interpreted by the various enzymes of prokaryotic or eukaryotic cells, so that the genes contained in the recombinant DNA can be expressed and the protein products produced.
The recombination can involve the DNA from two eukaryotic organisms, two prokaryotic organisms, or between an eukaryote and a prokaryote. An example of the latter is the production of human insulin by the bacterium E .COLI, which has been achieved by splicing the gene for insulin into the E. coli genome such that the insulin gene is expressed and the protein product formed.
DNA from different organisms of the same species combines together naturally to yield an organism that has traits from both parent organisms. There is also evidence accumulating that DNA transfer between different species may be a natural process. However, much interspecies mixing of DNA is the result of deliberate experimental manipulations.
A crucial process of these manipulations is the preparation of recombinant DNA. Recombinant DNA is DNA from different organisms that have been chemically bonded together to form a single DNA. The recombinant DNA can be interpreted by the various enzymes of prokaryotic or eukaryotic cells, so that the genes contained in the recombinant DNA can be expressed and the protein products produced.
The recombination can involve the DNA from two eukaryotic organisms, two prokaryotic organisms, or between an eukaryote and a prokaryote. An example of the latter is the production of human insulin by the bacterium E .COLI, which has been achieved by splicing the gene for insulin into the E. coli genome such that the insulin gene is expressed and the protein product formed.
Molecular Biology
Molecular biology is an interdisciplinary approach to understanding biological functions and regulation at the level of molecules such as nucleic acids, proteins, and carbohydrates Following the rapid advances in biological science brought about by the development and advancement of the Watson-Crick model of DNA (deoxyribonucleic acid) during the 1950s and 1960s, molecular biologists studied gene structure and function in increasing detail. In addition to advances in understanding genetic machinery and its regulation, molecular biologists continue to make fundamental and powerful discoveries regarding the structure and function of cells and of the mechanisms of genetic transmission. The continued study of these processes by molecular biologists and the advancement of molecular biological techniques requires integration of knowledge derived from physics, chemistry, mathematics, genetics, biochemistry, cell biology and other scientific fields.
Molecular biology also involves organic chemistry, physics , and biophysical chemistry as it deals with the physicochemical structure of macromolecules (nucleic acids, proteins, lipids, and carbohydrates) and their interactions. Genetic materials including DNA in most of the living forms orRNA (ribonucleic acid) in all plant viruses and in some animal viruses remain the subjects of intense study.
In 1945, William Astbury coined the term "molecular biology" referring to the study of the chemical and physical structure of biological macromolecules (large sized molecules). There was and still is a strong belief that all forms of life have uniformity in biological processes. The pioneer findings in prokaryotes (a simple or primitive cell type, e.g., bacteria and blue green alga) are extended to eukaryotes (a complex or well developed cell type, e.g., animal and plant cells).
The complete set of instructions for making an organism (i.e., the complete set of genes) is called its genome. It contains the master blueprint for all cellular structures and activities for the lifetime of the cell or organism. The human genome consists of tightly coiled threads of deoxyribonucleic acid (DNA) and associated protein molecules organized into structures called chromosomes. In humans, as in other higher organisms, a DNA molecule consists of two strands that wrap around each other to resemble a twisted ladder whose sides, made of sugar and phosphate molecules, are connected by rungs of nitrogen-containing chemicals called bases. Each strand is a linear arrangement of repeating similar units called nucleotides, which are each composed of one sugar, one phosphate, and a nitrogenous base. Four different bases are present in DNA adenine (A), thymine (T), cytosine (C), and guanine (G). The particular order of the bases arranged along the sugar-phosphate backbone is called the DNA sequence; the sequence specifies the exact genetic instructions required to create a particular organism with its own unique traits.
Each time a cell divides into two daughter cells, its full genome is duplicated; for humans and other complex organisms, this duplication occurs in the nucleus. During cell division the DNA molecule unwinds and the weak bonds between the base pairs break, allowing the strands to separate. Each strand directs the synthesis of a complementary new strand, with free nucleotides matching up with their complementary bases on each of the separated strands. Strict base-pairing rules are adhered to. Adenine will pair only with thymine (an A-T pair) and cytosine with guanine (a C-G pair). Each daughter cell receives one old and one new DNA strand. The cells adherence to these base-pairing rules ensures that the new strand is an exact copy of the old one. This minimizes the incidence of errors (mutations) that may greatly affect the resulting organism or its offspring.
Each DNA molecule contains many genes, the basic physical and functional units of heredity. A gene is a specific sequence of nucleotide bases, whose sequences carry the information required for constructing proteins, which provide the structural components of cells and tissues as well as enzymes for essential biochemical reactions.
The central dogma of molecular biology is that DNA is copied to make mRNA (messenger RNA) and mRNA is used as the template to make proteins. Formation of RNA is called transcription and formation of protein is called translation. Transcription and translation processes are regulated at various stages and the regulation steps are unique to prokaryotes and eukaryotes. DNA regulation determines what type and amount of mRNA should be transcribed, and this subsequently determines the type and amount of protein. This process is the bottom line for growth and morphogenesis.
Molecular biology also involves organic chemistry, physics , and biophysical chemistry as it deals with the physicochemical structure of macromolecules (nucleic acids, proteins, lipids, and carbohydrates) and their interactions. Genetic materials including DNA in most of the living forms orRNA (ribonucleic acid) in all plant viruses and in some animal viruses remain the subjects of intense study.
In 1945, William Astbury coined the term "molecular biology" referring to the study of the chemical and physical structure of biological macromolecules (large sized molecules). There was and still is a strong belief that all forms of life have uniformity in biological processes. The pioneer findings in prokaryotes (a simple or primitive cell type, e.g., bacteria and blue green alga) are extended to eukaryotes (a complex or well developed cell type, e.g., animal and plant cells).
The complete set of instructions for making an organism (i.e., the complete set of genes) is called its genome. It contains the master blueprint for all cellular structures and activities for the lifetime of the cell or organism. The human genome consists of tightly coiled threads of deoxyribonucleic acid (DNA) and associated protein molecules organized into structures called chromosomes. In humans, as in other higher organisms, a DNA molecule consists of two strands that wrap around each other to resemble a twisted ladder whose sides, made of sugar and phosphate molecules, are connected by rungs of nitrogen-containing chemicals called bases. Each strand is a linear arrangement of repeating similar units called nucleotides, which are each composed of one sugar, one phosphate, and a nitrogenous base. Four different bases are present in DNA adenine (A), thymine (T), cytosine (C), and guanine (G). The particular order of the bases arranged along the sugar-phosphate backbone is called the DNA sequence; the sequence specifies the exact genetic instructions required to create a particular organism with its own unique traits.
Each time a cell divides into two daughter cells, its full genome is duplicated; for humans and other complex organisms, this duplication occurs in the nucleus. During cell division the DNA molecule unwinds and the weak bonds between the base pairs break, allowing the strands to separate. Each strand directs the synthesis of a complementary new strand, with free nucleotides matching up with their complementary bases on each of the separated strands. Strict base-pairing rules are adhered to. Adenine will pair only with thymine (an A-T pair) and cytosine with guanine (a C-G pair). Each daughter cell receives one old and one new DNA strand. The cells adherence to these base-pairing rules ensures that the new strand is an exact copy of the old one. This minimizes the incidence of errors (mutations) that may greatly affect the resulting organism or its offspring.
Each DNA molecule contains many genes, the basic physical and functional units of heredity. A gene is a specific sequence of nucleotide bases, whose sequences carry the information required for constructing proteins, which provide the structural components of cells and tissues as well as enzymes for essential biochemical reactions.
The central dogma of molecular biology is that DNA is copied to make mRNA (messenger RNA) and mRNA is used as the template to make proteins. Formation of RNA is called transcription and formation of protein is called translation. Transcription and translation processes are regulated at various stages and the regulation steps are unique to prokaryotes and eukaryotes. DNA regulation determines what type and amount of mRNA should be transcribed, and this subsequently determines the type and amount of protein. This process is the bottom line for growth and morphogenesis.
DNA Microarray Technology
An array is an orderly arrangement of samples where matching of known and unknown DNA samples is done based on base pairing rules. An array experiment makes use of common assay systems such as microplates or standard blotting membranes. The sample spot sizes are typically less than 200 microns in diameter usually contain thousands of spots.
Thousands of spotted samples known as probes (with known identity) are immobilized on a solid support (a microscope glass slides or silicon chips or nylon membrane). The spots can be DNA, cDNA, or oligonucleotides. These are used to determine complementary binding of the unknown sequences thus allowing parallel analysis for gene expression and gene discovery. An experiment with a single DNA chip can provide information on thousands of genes simultaneously. An orderly arrangement of the probes on the support is important as the location of each spot on the array is used for the identification of a gene.
Types of Microarrays:
Depending upon the kind of immobilized sample used construct arrays and the information fetched, the Microarray experiments can be categorized in three ways:
1. Microarray expression analysis: In this experimental setup, the cDNA derived from the mRNA of known genes is immobilized. The sample has genes from both the normal as well as the diseased tissues. Spots with more more intensity are obtained for diseased tissue gene if the gene is over expressed in the diseased condition. This expression pattern is then compared to the expression pattern of a gene responsible for a disease.
2. Microarray for mutation analysis: For this analysis, the researchers use gDNA. The genes might differ from each other by as less as a single nucleotide base. A single base difference between two sequences is known as Single Nucleotide Polymorphism (SNP) and detecting them is known as SNP detection
3. Comparative Genomic Hybridization: It is used for the identification in the increase or decrease of the important chromosomal fragments harboring genes involved in a disease.
Applications of Microarrays:
Gene discovery: DNA Microarray technology helps in the identification of new genes, know about their functioning and expression levels under different conditions.
Disease diagnosis: DNA Microarray technology helps researchers learn more about different diseases such as heart diseases, mental illness, infectious disease and especially the study of cancer. Until recently, different types of cancer have been classified on the basis of the organs in which the tumors develop. Now, with the evolution of microarray technology, it will be possible for the researchers to further classify the types of cancer on the basis of the patterns of gene activity in the tumor cells. This will tremendously help the pharmaceutical community to develop more effective drugs as the treatment strategies will be targeted directly to the specific type of cancer.
Drug discovery: Microarray technology has extensive application in Pharmacogenomics.Pharmacogenomics is the study of correlations between therapeutic responses to drugs and the genetic profiles of the patients. Comparative analysis of the genes from a diseased and a normal cell will help the identification of the biochemical constitution of the proteins synthesized by the diseased genes. The researchers can use this information to synthesize drugs which combat with these proteins and reduce their effect.
Toxicological research: Microarray technology provides a robust platform for the research of the impact of toxins on the cells and their passing on to the progeny. Toxicogenomics establishes correlation between responses to toxicants and the changes in the genetic profiles of the cells exposed to such toxicants.
Thousands of spotted samples known as probes (with known identity) are immobilized on a solid support (a microscope glass slides or silicon chips or nylon membrane). The spots can be DNA, cDNA, or oligonucleotides. These are used to determine complementary binding of the unknown sequences thus allowing parallel analysis for gene expression and gene discovery. An experiment with a single DNA chip can provide information on thousands of genes simultaneously. An orderly arrangement of the probes on the support is important as the location of each spot on the array is used for the identification of a gene.
Types of Microarrays:
Depending upon the kind of immobilized sample used construct arrays and the information fetched, the Microarray experiments can be categorized in three ways:
1. Microarray expression analysis: In this experimental setup, the cDNA derived from the mRNA of known genes is immobilized. The sample has genes from both the normal as well as the diseased tissues. Spots with more more intensity are obtained for diseased tissue gene if the gene is over expressed in the diseased condition. This expression pattern is then compared to the expression pattern of a gene responsible for a disease.
2. Microarray for mutation analysis: For this analysis, the researchers use gDNA. The genes might differ from each other by as less as a single nucleotide base. A single base difference between two sequences is known as Single Nucleotide Polymorphism (SNP) and detecting them is known as SNP detection
3. Comparative Genomic Hybridization: It is used for the identification in the increase or decrease of the important chromosomal fragments harboring genes involved in a disease.
Applications of Microarrays:
Gene discovery: DNA Microarray technology helps in the identification of new genes, know about their functioning and expression levels under different conditions.
Disease diagnosis: DNA Microarray technology helps researchers learn more about different diseases such as heart diseases, mental illness, infectious disease and especially the study of cancer. Until recently, different types of cancer have been classified on the basis of the organs in which the tumors develop. Now, with the evolution of microarray technology, it will be possible for the researchers to further classify the types of cancer on the basis of the patterns of gene activity in the tumor cells. This will tremendously help the pharmaceutical community to develop more effective drugs as the treatment strategies will be targeted directly to the specific type of cancer.
Drug discovery: Microarray technology has extensive application in Pharmacogenomics.Pharmacogenomics is the study of correlations between therapeutic responses to drugs and the genetic profiles of the patients. Comparative analysis of the genes from a diseased and a normal cell will help the identification of the biochemical constitution of the proteins synthesized by the diseased genes. The researchers can use this information to synthesize drugs which combat with these proteins and reduce their effect.
Toxicological research: Microarray technology provides a robust platform for the research of the impact of toxins on the cells and their passing on to the progeny. Toxicogenomics establishes correlation between responses to toxicants and the changes in the genetic profiles of the cells exposed to such toxicants.
DNA Replication – The Replisome
The replisome is a complex molecular machine that carries out replication of DNA. It is comprised of a number of subcomponents, each performing a specific function during the process of replication. Helicase is an enzyme which breaks the hydrogen bonds between the two strands of DNA, thus separating the strands ahead of DNA synthesis. As helicase unwinds the double helix, it induces the formation of supercoils in other areas of the DNA.
Gyrase relaxes and undoes the supercoiling which has been caused by the helicase by cutting the DNA strands, allowing it to rotate and release the supercoil, and then rejoining the strands. Gyrase is most commonly located upstreak of the replication fork -- where the supercoils are being formed.
Primase adds complementary RNA primers to a DNA strand to begin Okazaki fragments. In addition, because DNA Polymerae can only continue (but not begin) a strand, Primase begins the leading strand as well.
DNA polymerase III is comprised of two catalytic cores -- one for replication of the leading strand and one for the lagging strand. DNA polemerase III, however, cannot stay on the DNA strand long enough to efficiently replicate a daughter strand. Hence, DNA polymerase III stays on the strands via a dimer beta clamp which contains three subunits that come together to enclose the strand -- ensuring that DNA polymerase III will remain on the strand for a few thousand nucleotides as opposed to a few hundred.
DNA polymerase I removes the RNA primers set by Primase and completes the Okazaki fragments. Because there is such a small gap remaining after the action of DNA polymerase I has continued the strand of the Okazaki fragment, ligase is required to fill in the gap. The two ends of the Okazaki fragments are subsequently connected by covalent bonds.
Single-strand binding proteins bind to the exposed bases in an effort to counteract their instability and prevent the single-strand DNA from hydrogen-bonding to itself to form dangerous hairpin structures.
DNA polymerases contain a ‘proofreading’ mechanism, commonly referred to as ‘exonuclease activity’. This removes nucleotides that have been mistakenly added.
DNA Replication – Signature of Design
DNA Replication stands as a fundamental challenge to those who seek to hold to a Darwinian worldview. As the process by which biological information is copied and passed on to succeeding generations, the mechanism is fundamental to the process of self-replication of cells. Yet self-replication of cells is necessary for the operation of any selective process such as natural selection. Thus, to attempt to explain the immense sophistication of this mechanism with reference to natural selection requires one to presuppose the existence of the very thing they wish to explain. Because of its extremely sophisticated nature, most biochemists previously reckoned that the system arose once, prior to the origin of the last universal common ancestor. In addition, many biochemists have long regarded the close functional similarity of DNA replication observed in all life as evidence for the single origin of DNA replication. Yet in 1999 researchers from the National Institutes of Health demonstrated that the core enzymes involved in the DNA replication machinery of bacteria and archae/eukaryotes (the two major trunks of the evolutionary tree of life) did not in fact share a common evolutionary origin. It thus appears as if two identical DNA replication systems have emerged independently in bacteria and archae -- after these two evolutionary lineages supposedly diverged from the last universal common ancestor.
It is phenomenal to think that this engineering marvel evolved a single time, let alone twice. There exists no obvious reason for DNA replication to take place by a semiconservative, RNA primer-dependent, bidirectional mechanism that depends on leading and lagging strands to produce DNA daughter molecules. Even if DNA replication could have evolved independently on two separate occasions, it is reasonable to expect that fundamentally different mechanisms would emerge for bacteria and the archae/eukaryotes given their idiosyncrasies. But, they did not.
Gyrase relaxes and undoes the supercoiling which has been caused by the helicase by cutting the DNA strands, allowing it to rotate and release the supercoil, and then rejoining the strands. Gyrase is most commonly located upstreak of the replication fork -- where the supercoils are being formed.
Primase adds complementary RNA primers to a DNA strand to begin Okazaki fragments. In addition, because DNA Polymerae can only continue (but not begin) a strand, Primase begins the leading strand as well.
DNA polymerase III is comprised of two catalytic cores -- one for replication of the leading strand and one for the lagging strand. DNA polemerase III, however, cannot stay on the DNA strand long enough to efficiently replicate a daughter strand. Hence, DNA polymerase III stays on the strands via a dimer beta clamp which contains three subunits that come together to enclose the strand -- ensuring that DNA polymerase III will remain on the strand for a few thousand nucleotides as opposed to a few hundred.
DNA polymerase I removes the RNA primers set by Primase and completes the Okazaki fragments. Because there is such a small gap remaining after the action of DNA polymerase I has continued the strand of the Okazaki fragment, ligase is required to fill in the gap. The two ends of the Okazaki fragments are subsequently connected by covalent bonds.
Single-strand binding proteins bind to the exposed bases in an effort to counteract their instability and prevent the single-strand DNA from hydrogen-bonding to itself to form dangerous hairpin structures.
DNA polymerases contain a ‘proofreading’ mechanism, commonly referred to as ‘exonuclease activity’. This removes nucleotides that have been mistakenly added.
DNA Replication – Signature of Design
DNA Replication stands as a fundamental challenge to those who seek to hold to a Darwinian worldview. As the process by which biological information is copied and passed on to succeeding generations, the mechanism is fundamental to the process of self-replication of cells. Yet self-replication of cells is necessary for the operation of any selective process such as natural selection. Thus, to attempt to explain the immense sophistication of this mechanism with reference to natural selection requires one to presuppose the existence of the very thing they wish to explain. Because of its extremely sophisticated nature, most biochemists previously reckoned that the system arose once, prior to the origin of the last universal common ancestor. In addition, many biochemists have long regarded the close functional similarity of DNA replication observed in all life as evidence for the single origin of DNA replication. Yet in 1999 researchers from the National Institutes of Health demonstrated that the core enzymes involved in the DNA replication machinery of bacteria and archae/eukaryotes (the two major trunks of the evolutionary tree of life) did not in fact share a common evolutionary origin. It thus appears as if two identical DNA replication systems have emerged independently in bacteria and archae -- after these two evolutionary lineages supposedly diverged from the last universal common ancestor.
It is phenomenal to think that this engineering marvel evolved a single time, let alone twice. There exists no obvious reason for DNA replication to take place by a semiconservative, RNA primer-dependent, bidirectional mechanism that depends on leading and lagging strands to produce DNA daughter molecules. Even if DNA replication could have evolved independently on two separate occasions, it is reasonable to expect that fundamentally different mechanisms would emerge for bacteria and the archae/eukaryotes given their idiosyncrasies. But, they did not.
Therapeutic Cloning
Somatic cell nuclear transfer can also be used to create a clonal embryo. The most likely scenario for this is to produce embryos for use in research, particularly stem cell research. This process is also called "research cloning" or "therapeutic cloning."
Therapeutic cloning is the production of human embryos for use in research. The goal of this process is not to create cloned human beings, but rather to harvest stem cells that can be used to study human development and to treat disease. Stem cells are important to biomedical researchers because they can be used to generate virtually any type of specialized cell in the human body. Stem cells are extracted from the egg after it has divided for 5 days. The egg at this stage of development is called a blastocyst. Many researchers hope that one day stem cells can be used to serve as replacement cells to treat heart disease, Alzheimer's, cancer, and other diseases.
Therapeutic cloning is the production of human embryos for use in research. The goal of this process is not to create cloned human beings, but rather to harvest stem cells that can be used to study human development and to treat disease. Stem cells are important to biomedical researchers because they can be used to generate virtually any type of specialized cell in the human body. Stem cells are extracted from the egg after it has divided for 5 days. The egg at this stage of development is called a blastocyst. Many researchers hope that one day stem cells can be used to serve as replacement cells to treat heart disease, Alzheimer's, cancer, and other diseases.
Hybrid & Chimeras
Hybrid animals are created when gametes (reproductive cells) from different species join to form a single embryo. A mule, for example, is the offspring of a female horse and a male donkey. Every cell in the body of hybrids contains genetic material from both parents.
Chimeras, named after creatures from Greek mythology, are created artificially by combining genetic material from different species into a single embryo. The adult animals that develop have different populations of cells that reflect different contributions from the species from which they were produced. Scientists have created the geep, for example, by combining genetic material from both a goat and a sheep.
Partially human hybrid embryos have been created by fusing human cells and animal eggs, and partially human chimeric embryos have been created by injecting human embryonic stem cells into animal embryos. Most scientists want to produce such embryos only for research, and oppose experiments that would allow human-animal chimeras to be brought to term.
The prospect of human-animal chimeras troubles many people and raises troubling questions about their moral and legal status. Would a human-animal chimera have human rights? Could it be patented and owned? What if it were 99.9% human and 0.1% chimpanzee?
Chimeras, named after creatures from Greek mythology, are created artificially by combining genetic material from different species into a single embryo. The adult animals that develop have different populations of cells that reflect different contributions from the species from which they were produced. Scientists have created the geep, for example, by combining genetic material from both a goat and a sheep.
Partially human hybrid embryos have been created by fusing human cells and animal eggs, and partially human chimeric embryos have been created by injecting human embryonic stem cells into animal embryos. Most scientists want to produce such embryos only for research, and oppose experiments that would allow human-animal chimeras to be brought to term.
The prospect of human-animal chimeras troubles many people and raises troubling questions about their moral and legal status. Would a human-animal chimera have human rights? Could it be patented and owned? What if it were 99.9% human and 0.1% chimpanzee?
SIGNAL TRANSDUCTION GENE THERAPY (STGT)
Signal transduction refers to the most common method of regulation of complex cell activity. It involves an external signal molecule (ligand) being bound by a specific cell's membrane receptor. The receptor, in turn triggers changes in the internal command system of the cell causing it to undertake a new activity so long as the ligand is present. A powerful new therapy using STGT is being developed whereby part of the genome of a common cold virus is replaced with:
1. A gene or genes that make a therapeutic chemical (e.g. hormone, cytokine etc.) and
2. A gene or genes that regulates the production of the therapeutic genes and that is itself "switched on" by a chemical that can be given to the patient.
In this procedure the patient is infected by the modified virus. The modified viral DNA then remains in the patient's cells. The therapy gene remain inactive until the "triggering" substance was given externally. The amount of triggering substance would determine the degree to which the therapy gene was turned on (like a dimmer switch).
1. A gene or genes that make a therapeutic chemical (e.g. hormone, cytokine etc.) and
2. A gene or genes that regulates the production of the therapeutic genes and that is itself "switched on" by a chemical that can be given to the patient.
In this procedure the patient is infected by the modified virus. The modified viral DNA then remains in the patient's cells. The therapy gene remain inactive until the "triggering" substance was given externally. The amount of triggering substance would determine the degree to which the therapy gene was turned on (like a dimmer switch).
Genomic DNAs
Genomic DNAs are unconnected from over 100 disparate manlike and fetal practice tissues, fallible pathological and tumor tissues, creep, rat, monkey, and lay tissues. Our genomic DNAs are provided prepared to use for SNP analysis, DNA methylation psychotherapy, reduplicate periodical variation (CNV) or comparative genomic hybridization (CGH) psychotherapy, Southern Blotting, and PCR. BioChain offers near any genomic DNAs from weak, pussyfoot, rat, monkey, opposite animals, and position tissues. Effort genomic DNAs from BioChain present prevent you invaluable search dimension to forthwith distinguish genes of relate; no longer give you requirement to adopt tissues and insulate genomic DNA by yourself.
The chronicle of DNA search is a tale of uncomplaining researchers busy day after day on myriad tiny problems. It is a tale of myriad answers assemblage at measure into profound insights. This is what happened with the Human Genome Projection.
The theme the HGP set out to answer was: What are all the genes in a imperfect being? The geneticists working on the Propel already knew a lot. They knew that genes use by manufacturing proteins. They knew that genes do this indirectly: Enzymes in the radiophone karyon move and unzip tune of a DNA multiply helix and make a assets of the DNA, a point sequence, into molecules of traveler RNA. The traveler RNA exits the karyon and carries the factor's cypher to cadre parts in the cytoplasm, to undeviating protein make. Eventually, the geneticists knew that humans change around 100,000 different types of proteins in their bodies. So researchers foreseen the HGP to move period, and to any Project geneticists devised new, speedier techniques for decipherment DNA. A lot sooner than expected, the healthy hominine genome was identified. And there weren't 100,000 genes-there were exclusive near 30,000! Or maybe only 25,000! A undignified conundrum: How do 100,000 proteins get manufactured by exclusive 25,000 genes?
Before the Hominine Genome Plan got started, something added had grow to illuminated: After a stuff of courier RNA is derived from a cistron, and before the traveler RNA leaves the room karyon, it gets "altered." Molecules titled spliceosomes cut the RNA message into fragments, take some of the fragments, and junction the put posterior unitedly again. The spliced message is what actually passes out of the cadre organelle into the cytoplasm, and gets translated into a accelerator.
But the spliced message isn't ever the unvaried. The set of fragments that get spliced unitedly can dissent. So that secondary proteins conclusion from the equal traveller RNA, and thence from the aforementioned sequence. So this is how 25,000 genes micturate 100,000 proteins.
How did this intricate group germinate? Whatever biologists believe the best active, reaction exploit molecules of lifespan were RNA's, patch others reckon they were proteins. Intriguingly, spliceosomes love few of both. Could deciding splicing be adjacent to the early molecules of invigoration? When we analyse this editing of RNA, are we perception far game into being's beginnings, virtuous as we see far support into the beginnings of the macrocosm when we canvass the oldest palish
The chronicle of DNA search is a tale of uncomplaining researchers busy day after day on myriad tiny problems. It is a tale of myriad answers assemblage at measure into profound insights. This is what happened with the Human Genome Projection.
The theme the HGP set out to answer was: What are all the genes in a imperfect being? The geneticists working on the Propel already knew a lot. They knew that genes use by manufacturing proteins. They knew that genes do this indirectly: Enzymes in the radiophone karyon move and unzip tune of a DNA multiply helix and make a assets of the DNA, a point sequence, into molecules of traveler RNA. The traveler RNA exits the karyon and carries the factor's cypher to cadre parts in the cytoplasm, to undeviating protein make. Eventually, the geneticists knew that humans change around 100,000 different types of proteins in their bodies. So researchers foreseen the HGP to move period, and to any Project geneticists devised new, speedier techniques for decipherment DNA. A lot sooner than expected, the healthy hominine genome was identified. And there weren't 100,000 genes-there were exclusive near 30,000! Or maybe only 25,000! A undignified conundrum: How do 100,000 proteins get manufactured by exclusive 25,000 genes?
Before the Hominine Genome Plan got started, something added had grow to illuminated: After a stuff of courier RNA is derived from a cistron, and before the traveler RNA leaves the room karyon, it gets "altered." Molecules titled spliceosomes cut the RNA message into fragments, take some of the fragments, and junction the put posterior unitedly again. The spliced message is what actually passes out of the cadre organelle into the cytoplasm, and gets translated into a accelerator.
But the spliced message isn't ever the unvaried. The set of fragments that get spliced unitedly can dissent. So that secondary proteins conclusion from the equal traveller RNA, and thence from the aforementioned sequence. So this is how 25,000 genes micturate 100,000 proteins.
How did this intricate group germinate? Whatever biologists believe the best active, reaction exploit molecules of lifespan were RNA's, patch others reckon they were proteins. Intriguingly, spliceosomes love few of both. Could deciding splicing be adjacent to the early molecules of invigoration? When we analyse this editing of RNA, are we perception far game into being's beginnings, virtuous as we see far support into the beginnings of the macrocosm when we canvass the oldest palish
Saturday, February 27, 2010
DNA Double Helix
DNA is a normally double stranded macromolecule. Two polynucleotide chains, held together by weak thermodynamic forces, form a DNA molecule.
Features of the DNA Double Helix
* Two DNA strands form a helical spiral, winding around a helix axis in a right-handed spiral
* The two polynucleotide chains run in opposite directions
* The sugar-phosphate backbones of the two DNA strands wind around the helix axis like the railing of a sprial staircase
* The bases of the individual nucleotides are on the inside of the helix, stacked on top of each other like the steps of a spiral staircase.
DNA Helix Axis
The helix axis is most apparent from a view directly down the axis. The sugar-phosphate backbone is on the outside of the helix where the polar phosphate groups (red and yellow atoms) can interact with the polar environment. The nitrogen (blue atoms) containing bases are inside, stacking perpendicular to the helix axis.
Features of the DNA Double Helix
* Two DNA strands form a helical spiral, winding around a helix axis in a right-handed spiral
* The two polynucleotide chains run in opposite directions
* The sugar-phosphate backbones of the two DNA strands wind around the helix axis like the railing of a sprial staircase
* The bases of the individual nucleotides are on the inside of the helix, stacked on top of each other like the steps of a spiral staircase.
DNA Helix Axis
The helix axis is most apparent from a view directly down the axis. The sugar-phosphate backbone is on the outside of the helix where the polar phosphate groups (red and yellow atoms) can interact with the polar environment. The nitrogen (blue atoms) containing bases are inside, stacking perpendicular to the helix axis.
DNA structure
DNA structure shows a variety of forms, both double-stranded and single-stranded. The mechanical properties of DNA, which are directly related to its structure, are a significant problem for cells. Every process which binds or reads DNA is able to use or modify the mechanical properties of DNA for purposes of recognition, packaging and modification. The extreme length (a chromosome may contain a 10 cm long DNA strand), relative rigidity and helical structure of DNA has led to the evolution of histones and of enzymes such as topoisomerases and helicases to manage a cell's DNA. The properties of DNA are closely related to its molecular structure and sequence, particularly the weakness of the hydrogen bonds and electronic interactions that hold strands of DNA together compared to the strength of the bonds within each strand.
Dna Structure
Experimental techniques which can directly measure the mechanical properties of DNA are relatively new, and high-resolution visualization in solution is often difficult. Nevertheless, scientists have uncovered large amount of data on the mechanical properties of this polymer, and the implications of DNA's mechanical properties on cellular processes is a topic of active current research.
The DNA found in many cells can be macroscopic in length - a few centimetres long for each human chromosome. Consequently, cells must compact or "package" DNA to carry it within them. In eukaryotes this is carried by spool-like proteins known as histones, around which DNA winds. It is the further compaction of this DNA-protein complex which produces the well known mitotic eukaryotic chromosomes.
Dna Structure
Experimental techniques which can directly measure the mechanical properties of DNA are relatively new, and high-resolution visualization in solution is often difficult. Nevertheless, scientists have uncovered large amount of data on the mechanical properties of this polymer, and the implications of DNA's mechanical properties on cellular processes is a topic of active current research.
The DNA found in many cells can be macroscopic in length - a few centimetres long for each human chromosome. Consequently, cells must compact or "package" DNA to carry it within them. In eukaryotes this is carried by spool-like proteins known as histones, around which DNA winds. It is the further compaction of this DNA-protein complex which produces the well known mitotic eukaryotic chromosomes.
Genetic testing
Point 1 Genetic testing permits Genetic diagnosis of diseases and vulnerability to a "child, S (genetic father) or a person's sex may determine paternity can be used. Normally, each person has two copies of a gene is one that her mother, one inherited from his father but will be taken. Human genome includes around 20,000 for the trust - is 25,000 genes.
Point 2 Individual gene and gene genetic diseases, genetic disorders that are associated with increasing risk of developing type variation for the possible presence of biochemical tests in the direction of a further level of chromosomes, including genetic testing than to study. Genetic testing identifies changes in chromosomes, genes or proteins. Generally, changes in testing that are associated with inherited disorders is found.
Point 3 A genetic test results confirm a suspected genetic condition or can cross out or to determine a "person of science or beyond is likely to help developing a genetic disorder. Coll several hundred genetic tests are common, and more are being developed.
Point 2 Individual gene and gene genetic diseases, genetic disorders that are associated with increasing risk of developing type variation for the possible presence of biochemical tests in the direction of a further level of chromosomes, including genetic testing than to study. Genetic testing identifies changes in chromosomes, genes or proteins. Generally, changes in testing that are associated with inherited disorders is found.
Point 3 A genetic test results confirm a suspected genetic condition or can cross out or to determine a "person of science or beyond is likely to help developing a genetic disorder. Coll several hundred genetic tests are common, and more are being developed.
Benefits of Genetic genealogy
Genetic genealogy gives the Genealogists, which are to examine or be supplemented means, their results of genealogy with the information, which is caught up over DNA examination. Positive test matches with another individual can:
* you put to positions for further descent research at the disposal
* assistance place ererbtes native country
* firmly discover you living relatives
* validate you existing research
* confirm you or refuse you assumed connections between families
* examine you or disprove you concerning theories sex
* you put to positions for further descent research at the disposal
* assistance place ererbtes native country
* firmly discover you living relatives
* validate you existing research
* confirm you or refuse you assumed connections between families
* examine you or disprove you concerning theories sex
Types of Genetic testing
• Newborn Screening: Newborn screening immediately after birth using genetic disorders that can be treated early in life are identified. Regular testing of children for some genetic disorders and the most widely used is Geprüftmillionen children every year in the United States are examined. Coll kid on the states considered Phenylketonuria (a genetic disorder that causes mental illness, if treatment) and congenital hypothyroidism (thyroid gland disorder of).
• Clinical trials: Clinical trials to determine the status of a specific genetic or chromosome, or hit out is used. In many cases, for genetic diagnosis were confirmed when a certain situation suggested the test was based on physical changes and symptoms. One person at any time during the clinical trials done 'can be, S life, but all the genes or genetic conditions is not available for all. Clinical trial results of a one-man, S. affect health care and disease management can choose.
• carrier testing: carrier testing people, a copy of a gene mutation which, if used to identify existing lift, two copies of a genetic disorder caused. Examination of such individuals a genetic disorder that people in ethnic groups have offered to family history and increased risk of specific genetic conditions. If both parents are tested, "made a pair is available, the risk of a child with a genetic condition S test report.
• Prenatal testing: one for pre-natal testing "to detect changes in the use of embryos, genes or chromosomes before birth is s. Examination of such a genetic or chromosomal disorder, with an increased risk of having a baby has offered to couples. In some cases, a prenatal test 'two, S-uncertainty may reduce or help them decide whether pregnancy terminates. Identify all possible inherited disorders and birth can not fault.
• Preimplantation genetic diagnosis: Genetic testing that the human embryo, before implantation as part of the processes are performing in vitro fertilization.
• East and presymptomatic testing: pre-determined, changes in gene identification and evaluation of presymptomatic forms often used in later life disorders that appear after birth are associated with. These tests are the people, a genetic disorder, with one family member can help, but whatever time you test a feature of the disorder is. Pre-determined test changes, a growing 'human, such as some types of cancer as a genetic basis, the possibility of developing disorders with S can be identified. Example, one person BRCA1, 65% cumulative risk of breast cancer have a change. Can determine whether a Presymptomatic testing person (an iron overload disorder) as developed hemochromatosis is a genetic disorder, no signs or symptoms first appear. Previous results and a specific disorder, presymptomatic testing and treatment in developing decision support available information about an individual's risks can provide.
• Judicial Review: Forensic testing uses DNA sequence identity of any person for the purposes authorized. Unlike the test described above, the use of judicial review that gene mutations are associated with illness is not identified. Testing of such crime or accident victims, to identify or exclude a biological relationship between people Verbrechenverdächtigen or installation means (eg, parenthood) can cross.
• Clinical trials: Clinical trials to determine the status of a specific genetic or chromosome, or hit out is used. In many cases, for genetic diagnosis were confirmed when a certain situation suggested the test was based on physical changes and symptoms. One person at any time during the clinical trials done 'can be, S life, but all the genes or genetic conditions is not available for all. Clinical trial results of a one-man, S. affect health care and disease management can choose.
• carrier testing: carrier testing people, a copy of a gene mutation which, if used to identify existing lift, two copies of a genetic disorder caused. Examination of such individuals a genetic disorder that people in ethnic groups have offered to family history and increased risk of specific genetic conditions. If both parents are tested, "made a pair is available, the risk of a child with a genetic condition S test report.
• Prenatal testing: one for pre-natal testing "to detect changes in the use of embryos, genes or chromosomes before birth is s. Examination of such a genetic or chromosomal disorder, with an increased risk of having a baby has offered to couples. In some cases, a prenatal test 'two, S-uncertainty may reduce or help them decide whether pregnancy terminates. Identify all possible inherited disorders and birth can not fault.
• Preimplantation genetic diagnosis: Genetic testing that the human embryo, before implantation as part of the processes are performing in vitro fertilization.
• East and presymptomatic testing: pre-determined, changes in gene identification and evaluation of presymptomatic forms often used in later life disorders that appear after birth are associated with. These tests are the people, a genetic disorder, with one family member can help, but whatever time you test a feature of the disorder is. Pre-determined test changes, a growing 'human, such as some types of cancer as a genetic basis, the possibility of developing disorders with S can be identified. Example, one person BRCA1, 65% cumulative risk of breast cancer have a change. Can determine whether a Presymptomatic testing person (an iron overload disorder) as developed hemochromatosis is a genetic disorder, no signs or symptoms first appear. Previous results and a specific disorder, presymptomatic testing and treatment in developing decision support available information about an individual's risks can provide.
• Judicial Review: Forensic testing uses DNA sequence identity of any person for the purposes authorized. Unlike the test described above, the use of judicial review that gene mutations are associated with illness is not identified. Testing of such crime or accident victims, to identify or exclude a biological relationship between people Verbrechenverdächtigen or installation means (eg, parenthood) can cross.
Helicases
Helicases are a class of enzymes vital to all living organisms. They are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands (i.e. DNA, RNA, or RNA-DNA hybrid) using energy derived from ATP hydrolysis.
Many cellular processes (DNA replication, transcription, translation, recombination, DNA repair, ribosome biogenesis) involve the separation of nucleic acid strands. Helicases are often utilized to separate strands of a DNA double helix or a self-annealed RNA molecule using the energy from ATP hydrolysis, a process characterized by the breaking of hydrogen bonds between annealed nucleotide bases. They move incrementally along one nucleic acid strand of the duplex with a directionality and processivity specific to each particular enzyme. There are many helicases (14 confirmed in E. coli, 24 in human cells) resulting from the great variety of processes in which strand separation must be catalyzed.
Helicases adopt different structures and oligomerization states. Whereas DnaB-like helicases unwind DNA as donut shaped hexamers, other enzymes have been shown to be active as monomers or dimers. Studies have shown that helicases may act passively, waiting for uncatalyzed unwinding to take place and then translocating between displaced strands, or can play an active role in catalyzing strand separation using the energy generated in ATP hydrolysis. In the latter case, the helicase acts comparably to an active motor, unwinding and translocating along its substrate as a direct result ATPase activity.. Helicases may process much faster in vivo than in vitro due to the presence of accessory proteins that aid in the destabilization of the fork junction.
Defects in the gene that codes helicase cause Werner syndrome, a disorder characterized by the appearance of premature aging.
Many cellular processes (DNA replication, transcription, translation, recombination, DNA repair, ribosome biogenesis) involve the separation of nucleic acid strands. Helicases are often utilized to separate strands of a DNA double helix or a self-annealed RNA molecule using the energy from ATP hydrolysis, a process characterized by the breaking of hydrogen bonds between annealed nucleotide bases. They move incrementally along one nucleic acid strand of the duplex with a directionality and processivity specific to each particular enzyme. There are many helicases (14 confirmed in E. coli, 24 in human cells) resulting from the great variety of processes in which strand separation must be catalyzed.
Helicases adopt different structures and oligomerization states. Whereas DnaB-like helicases unwind DNA as donut shaped hexamers, other enzymes have been shown to be active as monomers or dimers. Studies have shown that helicases may act passively, waiting for uncatalyzed unwinding to take place and then translocating between displaced strands, or can play an active role in catalyzing strand separation using the energy generated in ATP hydrolysis. In the latter case, the helicase acts comparably to an active motor, unwinding and translocating along its substrate as a direct result ATPase activity.. Helicases may process much faster in vivo than in vitro due to the presence of accessory proteins that aid in the destabilization of the fork junction.
Defects in the gene that codes helicase cause Werner syndrome, a disorder characterized by the appearance of premature aging.
DNA polymerase
A DNA polymerase is an enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. DNA polymerases are best-known for their role in DNA replication, in which the polymerase "reads" an intact DNA strand as a template and uses it to synthesize the new strand. The newly-polymerized molecule is complementary to the template strand and identical to the template's original partner strand.
DNA polymerases use a magnesium ion for catalytic activity.
DNA polymerase can add free nucleotides to only the 3’ end of the newly-forming strand. This results in elongation of the new strand in a 5'-3' direction. No known DNA polymerase is able to begin a new chain (de novo). DNA polymerase can add a nucleotide onto only a preexisting 3'-OH group, and, therefore, needs a primer at which it can add the first nucleotide. Primers consist of RNA and DNA bases with the first two bases always being RNA, and are synthesized by another enzyme called primase. An enzyme known as a helicase is required to unwind DNA from a double-strand structure to a single-strand structure to facilitate replication of each strand consistent with the semiconservative model of DNA replication.
Error correction is a property of some, but not all, DNA polymerases. This process corrects mistakes in newly-synthesized DNA. When an incorrect base pair is recognized, DNA polymerase reverses its direction by one base pair of DNA. The 3'->5' exonuclease activity of the enzyme allows the incorrect base pair to be excised Following base excision, the polymerase can re-insert the correct base and replication can continue.
DNA polymerases use a magnesium ion for catalytic activity.
DNA polymerase can add free nucleotides to only the 3’ end of the newly-forming strand. This results in elongation of the new strand in a 5'-3' direction. No known DNA polymerase is able to begin a new chain (de novo). DNA polymerase can add a nucleotide onto only a preexisting 3'-OH group, and, therefore, needs a primer at which it can add the first nucleotide. Primers consist of RNA and DNA bases with the first two bases always being RNA, and are synthesized by another enzyme called primase. An enzyme known as a helicase is required to unwind DNA from a double-strand structure to a single-strand structure to facilitate replication of each strand consistent with the semiconservative model of DNA replication.
Error correction is a property of some, but not all, DNA polymerases. This process corrects mistakes in newly-synthesized DNA. When an incorrect base pair is recognized, DNA polymerase reverses its direction by one base pair of DNA. The 3'->5' exonuclease activity of the enzyme allows the incorrect base pair to be excised Following base excision, the polymerase can re-insert the correct base and replication can continue.
DNA topoisomerase:
DNA topoisomerase DNA supercoiling changes. Reduction of DNA-DNA topoisomerase. Type of DNA topoisomerase I drop a hair and DNA topoisomerase II-type knife with two teeth. DNA Topoisomerase regulates DNA supercoiling. Help topoisomerase DNA transcription and replication of DNA. And DNA topoisomerase I and DNA topoisomerase II, a DNA topoisomerase DNA topoisomerase III and IV.
DNA topoisomerase: DNA topoisomerase is an enzyme that changes the supercoiling of double DNA. DNA topoisomerase acts for a short cut one or both strands of DNA. DNA topoisomerase type I series of cuts and the level of DNA topoisomerase II knife with two strands of DNA. Coil leave DNA topoisomerase and extends the DNA molecule. DNA topoisomerase helps regulate DNA supercoiling. DNA topoisomerase using DNA replication and transcription. Just as DNA topoisomerase I and DNA topoisomerase II, a DNA topoisomerase DNA topoisomerase III and IV. DNA topoisomerase III may regulate recombination. DNA topoisomerase IV regulates the separation of newly replicated chromosomes.
DNA topoisomerase: DNA topoisomerase is an enzyme that changes the supercoiling of double DNA. DNA topoisomerase acts for a short cut one or both strands of DNA. DNA topoisomerase type I series of cuts and the level of DNA topoisomerase II knife with two strands of DNA. Coil leave DNA topoisomerase and extends the DNA molecule. DNA topoisomerase helps regulate DNA supercoiling. DNA topoisomerase using DNA replication and transcription. Just as DNA topoisomerase I and DNA topoisomerase II, a DNA topoisomerase DNA topoisomerase III and IV. DNA topoisomerase III may regulate recombination. DNA topoisomerase IV regulates the separation of newly replicated chromosomes.
Types of Gene Therapy
Gene therapy
is the insertion of genes into an individual's cells and tissues to treat a disease, and hereditary diseases in which a defective mutant allele is replaced with a functional one. Although the technology is still in its infancy, it has been used with some success. Antisense therapy is not strictly a form of gene therapy, but is a genetically-mediated therapy and is often considered together with other methods.
How does gene therapy work?
In most gene therapy studies, a "normal" gene is inserted into the genome to replace an "abnormal," disease-causing gene. A carrier molecule called a vector must be used to deliver the therapeutic gene to the patient's target cells. Currently, the most common vector is a virus that has been genetically altered to carry normal human DNA. Viruses have evolved a way of encapsulating and delivering their genes to human cells in a pathogenic manner. Scientists have tried to take advantage of this capability and manipulate the virus genome to remove disease-causing genes and insert therapeutic genes.
Target cells such as the patient's liver or lung cells are infected with the viral vector. The vector then unloads its genetic material containing the therapeutic human gene into the target cell. The generation of a functional protein product from the therapeutic gene restores the target cell to a normal state.
How is gene therapy being studied in the treatment of cancer?
Researchers are studying several ways to treat cancer using gene therapy. Some approaches target healthy cells to enhance their ability to fight cancer. Other approaches target cancer cells, to destroy them or prevent their growth. Some gene therapy techniques under study are described below. In one approach, researchers replace missing or altered genes with healthy genes.
The types of gene therapy described thus far all have one factor in common: that is, that the tissues being treated are somatic (somatic cells include all the cells of the body, excluding sperm cells and egg cells). In contrast to this is the replacement of defective genes in the germline cells (which contribute to the genetic heritage of the offspring). Gene therapy in germline cells has the potential to affect not only the individual being treated, but also his or her children as well. Germline therapy would change the genetic pool of the entire human species, and future generations would have to live with that change.
Gene Therapy: requirements
The gene must be identified and cloned. This has been done for the ADA gene.It must be inserted in cells that can take up long-term residence in the patient. So far, this means removing the patient's own cells, treating them in tissue culture, and then returning them to the patient. It must be inserted in the DNA so that it will be expressed adequately; that is, transcribed and translated with sufficient efficiency that worthwhile amounts of the enzyme are produced. All these requirements seem to have been met for SCID therapy using a retrovirus as the gene vector. Retroviruses have several advantages for introducing genes into human cells. Their envelope protein enables the virus to infect human cells. RNA copies of the human ADA gene can be incorporated into the retroviral genome using a packaging cell.
is the insertion of genes into an individual's cells and tissues to treat a disease, and hereditary diseases in which a defective mutant allele is replaced with a functional one. Although the technology is still in its infancy, it has been used with some success. Antisense therapy is not strictly a form of gene therapy, but is a genetically-mediated therapy and is often considered together with other methods.
How does gene therapy work?
In most gene therapy studies, a "normal" gene is inserted into the genome to replace an "abnormal," disease-causing gene. A carrier molecule called a vector must be used to deliver the therapeutic gene to the patient's target cells. Currently, the most common vector is a virus that has been genetically altered to carry normal human DNA. Viruses have evolved a way of encapsulating and delivering their genes to human cells in a pathogenic manner. Scientists have tried to take advantage of this capability and manipulate the virus genome to remove disease-causing genes and insert therapeutic genes.
Target cells such as the patient's liver or lung cells are infected with the viral vector. The vector then unloads its genetic material containing the therapeutic human gene into the target cell. The generation of a functional protein product from the therapeutic gene restores the target cell to a normal state.
How is gene therapy being studied in the treatment of cancer?
Researchers are studying several ways to treat cancer using gene therapy. Some approaches target healthy cells to enhance their ability to fight cancer. Other approaches target cancer cells, to destroy them or prevent their growth. Some gene therapy techniques under study are described below. In one approach, researchers replace missing or altered genes with healthy genes.
The types of gene therapy described thus far all have one factor in common: that is, that the tissues being treated are somatic (somatic cells include all the cells of the body, excluding sperm cells and egg cells). In contrast to this is the replacement of defective genes in the germline cells (which contribute to the genetic heritage of the offspring). Gene therapy in germline cells has the potential to affect not only the individual being treated, but also his or her children as well. Germline therapy would change the genetic pool of the entire human species, and future generations would have to live with that change.
Gene Therapy: requirements
The gene must be identified and cloned. This has been done for the ADA gene.It must be inserted in cells that can take up long-term residence in the patient. So far, this means removing the patient's own cells, treating them in tissue culture, and then returning them to the patient. It must be inserted in the DNA so that it will be expressed adequately; that is, transcribed and translated with sufficient efficiency that worthwhile amounts of the enzyme are produced. All these requirements seem to have been met for SCID therapy using a retrovirus as the gene vector. Retroviruses have several advantages for introducing genes into human cells. Their envelope protein enables the virus to infect human cells. RNA copies of the human ADA gene can be incorporated into the retroviral genome using a packaging cell.
DNA and RNA- The Strands of Life
Deoxyribonucleic Acid (DNA) is the component in a cell that is responsible for, perhaps, all functions within the cell and the organism. DNA stores and passes down information from one generation to the next. This is known as the genetic code.
DNA is a molecule, comprised of nucleotides, the monomers of DNA. Each nucleotide contains a phosphate group, a five-carbon sugar, and a nitrogen base. The five-carbon sugar in DNA is called deoxyribose. Each nucleotide will contain one of four n-bases: guanine, adenine, cytosine, and thymine. Guanine and Adenine are called purines, while cytosine and thymine are pyrimidines. In the structural formula for purines, there are two rings made up of nitrogen and in the pyrimidines, there is one ring made up of nitrogen.
The shape of DNA is a double helix, proposed by James Watson and Francis Crick. The name describes DNA's two strands that are twisted around one another. Base-pairing holds these two strands together. In base pairing, each nitrogen base of one of the strands bonds with a weak hydrogen bond to the n-base of another strand. guanine bonds with cytosine and adenine bonds with thymine. These n-bases form the "rungs" of the double helix or "twisted ladder." The sugar and phosphate groups form the outside of the ladder. The nitrogen bases are always bonded to the sugar. This base-sugar unit is referred to as a nucleoside. The phosphate groups link sugars together.
The process by which DNA copies itself is called replication. It is necessary for DNA to replicate to produce another generation. During replication, the DNA untwists itself. The weak hydrogen bonds between each of the n-bases break down the center. A new, complimentary nucleotide is placed with the orginal strand to form the new DNA. Finally the DNA coils again to its orginal shape.
Ribonucleic Acid (RNA) can be compared to an employer and an employee. DNA is the employer and RNA works for it. DNA does not leave the nucleus of a cell, so it must have a messanger to carry the genetic code to other places in the cell. RNA is much like DNA except the following things: RNA is a single strand and it contails uracil, rather than thymine. There are three types of RNA: messanger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). Each has a specific purpose to carry out in the cell. The mRNA is made up of codons, a set of three n-bases. Each codon links to the original DNA strand and reads the genetic code by a process called transcription. The mRNA carries this message out of the nucleus and into the cytoplasm of the cell. tRNA bonds to mRNA with a peptide bond. tRNA is made up of anti-codons. These anti-codons bond to the codons, which tells them to pick up an amino acid, the monomer of proteins. After the amino acids are gathered, they build on the ribosomes, organelles that are made up of rRNA, of the cell. The ribosomes create proteins by a process known as protein synthesis. This process is probably the most important function of the DNA because proteins are the most important things in sustaining life.
DNA is not completely understood by scientists at this time. The more we can learn, the more genetic disorders we may prevent, and the more knowledge about life we will gain.
DNA is a molecule, comprised of nucleotides, the monomers of DNA. Each nucleotide contains a phosphate group, a five-carbon sugar, and a nitrogen base. The five-carbon sugar in DNA is called deoxyribose. Each nucleotide will contain one of four n-bases: guanine, adenine, cytosine, and thymine. Guanine and Adenine are called purines, while cytosine and thymine are pyrimidines. In the structural formula for purines, there are two rings made up of nitrogen and in the pyrimidines, there is one ring made up of nitrogen.
The shape of DNA is a double helix, proposed by James Watson and Francis Crick. The name describes DNA's two strands that are twisted around one another. Base-pairing holds these two strands together. In base pairing, each nitrogen base of one of the strands bonds with a weak hydrogen bond to the n-base of another strand. guanine bonds with cytosine and adenine bonds with thymine. These n-bases form the "rungs" of the double helix or "twisted ladder." The sugar and phosphate groups form the outside of the ladder. The nitrogen bases are always bonded to the sugar. This base-sugar unit is referred to as a nucleoside. The phosphate groups link sugars together.
The process by which DNA copies itself is called replication. It is necessary for DNA to replicate to produce another generation. During replication, the DNA untwists itself. The weak hydrogen bonds between each of the n-bases break down the center. A new, complimentary nucleotide is placed with the orginal strand to form the new DNA. Finally the DNA coils again to its orginal shape.
Ribonucleic Acid (RNA) can be compared to an employer and an employee. DNA is the employer and RNA works for it. DNA does not leave the nucleus of a cell, so it must have a messanger to carry the genetic code to other places in the cell. RNA is much like DNA except the following things: RNA is a single strand and it contails uracil, rather than thymine. There are three types of RNA: messanger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). Each has a specific purpose to carry out in the cell. The mRNA is made up of codons, a set of three n-bases. Each codon links to the original DNA strand and reads the genetic code by a process called transcription. The mRNA carries this message out of the nucleus and into the cytoplasm of the cell. tRNA bonds to mRNA with a peptide bond. tRNA is made up of anti-codons. These anti-codons bond to the codons, which tells them to pick up an amino acid, the monomer of proteins. After the amino acids are gathered, they build on the ribosomes, organelles that are made up of rRNA, of the cell. The ribosomes create proteins by a process known as protein synthesis. This process is probably the most important function of the DNA because proteins are the most important things in sustaining life.
DNA is not completely understood by scientists at this time. The more we can learn, the more genetic disorders we may prevent, and the more knowledge about life we will gain.
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