Chapter 8, Transposition Summary and Analysis

McClintock continues her experimentation on plants at Cold Spring Harbor. She has developed some unusual mutations in plants with a high degree of genetic instability. The maize she grew had varied colors, each splotch of which represented division from a single mutated cell. The number of patches of a particular size indicated the frequency of mutation during the seed's development. The appearance of the corn allowed McClintock to generate a history of the seed's development. She found that if a plant exhibited a high rate of mutation early in its development, that it would maintain this rate of mutation throughout its life - this held for high and low levels of mutation. McClintock knew then that something was regulating the mutation rate. She was one of the first to discover this phenomenon, and became obsessed with understanding the mechanism...