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Rapid Growth In Genetics: The second period of rapid growth in genetics began after World War II and continues to this day. In this period, geneticists have sought to understand the mechanisms of genetics on a finer scale than had earlier been possible. They have looked for the answers to such questions as: Of what is a gene made? How does it affect the rest of the cell? What turns it on or off? Most of these questions have now been answered, at least in part, and the answers have turned out to entail as much chemical as biological information.
In 1950, when the more recent period of rapid growth in genetics began, it appeared likely that all of the detailed instructions needed to produce an organism, even one as complicated as a human being, must be contained in the two sets of genes that the organism inherits from its parents. One set of genes comes from the unfertilized egg of the mother, the other from the sperm of the father.
The second category, physiological genetics, deals with the nature and action of the gene. It includes such specialty fields as (1) mutation genetics, the study of induced and spontaneous mutations; (2) biochemical genetics, the study of the chemical nature of hereditary materials; and (3) developmental genetics (or phenoge-netics), the study of the relationship between genes and the development of character.
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