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.