GENOMICS: REVOLUTIONIZING MEDICINE

The Highly Ordered Universe of the Genome

In a truly elegant melding of form and function, DNA contains instructions, in coded form, necessary to produce and maintain a functioning organism or biological agent. Some pathogens such as HIV encode their instructions in RNA rather than in DNA. These instructions appear in viral genomes, chromosomes, and plasmids, which are extra-chromosomal units of DNA. The only "letters" to the code are four nucleotide bases — adenine (A), thymine (T), guanine (G) and cytosine (C). These bases — "read" three at a time — are able to code for the standard 20 amino acids from which proteins are made. The process is not direct (there are intermediaries), but it is predictable. There are also codes to initiate and stop the production of proteins, as well as other regulatory codes, and "junk" DNA, so named because it has no obvious function.

Automated DNA sequencer. 3-D Model by Bill Pietsch.

The genomic sequences contain the information needed to make and maintain an organism and are thus of great importance. But sequencing is merely an interim step to the ultimate goal — which is to understand every function of every portion of the genome and to determine every structure encoded by it.

Autoradiogram. This particular autoradiogram contains the sequences of several different fragments of human DNA. The sequences are read in columns from the bottom up. Each column has four lanes — one for each base — that indicate the presence or absence of a particular base at any given point in the sequence. Though still sometimes used, this type of readout originated from manual sequencing methods, which now have largely been automated.