September 7, 2003

DNA, or deoxyribonucleic acid, is contained inside all living things. DNA contains the necessary instructions for protein synthesis and replication. Protein synthesis is the production of protein, which is used by cells or viruses for development. Replication is the process by which DNA copies itself for each replication or virus, passing on the information needed for the protein synthesis. The nucleuses of cells contain DNA, which is stored on chromosomes.

A molecule of DNA is in the shape of a double helix, or two spiral staircases wrapped around each other. These two chains are composed of chemical compounds, which are called nucleotides. Each nucleotide has three parts; a sugar molecule called deoxyribose, a phosphate group and a base, which contains nitrogen. There are four different bases called adenine, thymine, guanine and cytostine. The 2 molecules then bind, combining the 2 bases, as follows: adenine pairs with thymine, and guanine pairs with cytostine. These bases join by what is called a hydrogen bond.

Francis Crick, a British Biophysicist and James D. Watson, an American Biochemist discovered DNA in 1953. They won the 1962 Nobel Prize for their work. Their model educated people for the first time about DNA, and the understanding of protein synthesis.

DNA sequencing can be used to determine the order of the nucleotide bases inside individual strands of DNA. Most versions of DNA sequencing use a technique called primer extension. With primer extension, small peices of DNA are copied and tailored, so that each DNA segment ends in one of the four different nucleotide bases. Scientists have successfully done this with the genetic material of several microorganisms. In 1998, scientists actually sequenced the entire genome of a multicellular organism, a roundworm. The Human Genome Project has now been created to determine the order of the three billion nucleotide bases that make up human genetic matter.