Mapping the Human Genome

The science of genetics has evolved dramatically since Mendel deduced several important principles of inheritance by observing the color of pea seeds. From the visual observation of phenotypic characteristics, steady progress has taken us ever closer to the molecular basis for gene expression — the DNA sequences of individual cells. For several years, molecular geneticists were preoccupied with the biochemical characterization of mutant enzymes and other cell products; recently, more attention has been directed to the study of nucleic acid molecules containing particular gene or messenger RNA (mRNA) sequences. In this issue of the Journal, Orkin and his co-workers show . . .