ABSTRACT
The functional unit of information in living systems is the gene. A gene is de ned biochemically as a segment of deoxyribonucleic acid (DNA) (or, in a few cases, ribonucleic acid, RNA) that encodes the information required to produce a functional biological product-a protein. Genetic theory contributed the concept of coding by genes. Physics permitted the determination of molecular structure by x-ray diffraction analysis. Chemistry revealed the composition of nucleic acids and proteins.1 These and other major advances gave rise to the central dogma of molecular biology comprising the three major processes in the cellular utilization of genetic information. The rst is replication, the copying of parental DNA to form daughter DNA molecules with identical nucleotide
sequences. The second is transcription, the process by which parts of the genetic message encoded in DNA are copied precisely into RNA. The third is translation, whereby the genetic message encoded in messenger RNA is translated on the ribosome into a polypeptide with a particular sequence of amino acids.
