The End of the Beginning

摘要

In classical experimental genetics, where many of us began, we could not assert the existence of a wild-type gene until a mutant version with an altered function had been isolated. For Mendel to say that there was a factor for tallness, he first had to find heritable dwarf variants that suffered from a lack of tallness. This genetics began with inherited changes in phenotype that provided, if not knowledge, then at least a classification of the functions of genes, and it used genetic complementation experiments to discover how many genes were involved in dictating each phenotype. But, if one asked how many genes were required to make a bacteriophage or a bacterium or a fly or a mouse, no answer could be given.