The Regulation of Recombination in Plants
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Excerpt
The Adaptive Nature of the Genetic System
The study of adaptation has traditionally been focused on the external form and coloration of organisms. Adaptations of a strictly physiological nature have been examined in a fewer number of cases. To the classical examples of adaptation, such as mimicry, protective coloration, and the contrivances for pollination and seed dispersal, have been added in recent decades such physiological examples as the climatic and edaphic ecotypes in higher plants, and the poison-resistant strains in bacteria and insects. It has usually been assumed in inquiries into the origin of morphological and physiological adaptations that the hereditary mechanism is a constant factor. This facile assumption can no longer be maintained.
The first indication that the mechanism of heredity and variation is not fixed and immutable came with the discovery that its component features—the mutation rate, chiasma frequency, course of meiosis, fertility, type of breeding system, and...
