Genomics

With easy DNA sequencing technology comes the possibility to determine all the information present in the DNA of a single organism—the entire sequence of its DNA. Genomics is the study of an organism's entire information content. In humans, that amounts to about 3 billion base pairs of information, or about 10 million sequencing experiments (although it isn't nearly all that efficient). More to the point is the sequence information in a small bacterium, about 4 to 5 million base pairs of information. This is much more feasible, and can be accomplished in about 10,000 to 20,000 separate experiments—a few weeks' worth of information gathering in a big, dedicated laboratory. The strategy is sometimes called “shotgun sequencing,” because the information-gathering process isn't precisely aimed. Rather, a random set of clones is made in a bacteriophage-like vector (called acosmid) and a mini-library of DNA inserts is made in a plasmid vector. These recombinant plasmids are then used as templates for sequencing reactions such as the ones described earlier. The sequences are analyzed by computer so that the overlapping DNA sequences can be fit together to make longer sequences. This step-by-step process is continued until enough information is gathered to assemble a whole sequence of the DNA for an organism or chromosome. Although the shotgun technique may lead to a single stretch of sequence being determined several times before all the sequences are determined, it is faster than trying to order each clone and then determine their sequences individually.

Scientists have determined complete genomic sequences for a number of viruses, over fifteen bacteria, and laboratory yeast. Many pharmaceutical companies are interested in the sequence information from bacteria that cause disease, in the hopes that the information obtained will lead to new drug targets.