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chromosomal duplication be an operator controlled by the sensor; i.e., whenever the sensor is deactivated, intrachromosomal duplication takes place on the sets of genes associated with the sensor. In consequence, disappearance of the environmental feature will result in many copies of the genes, and hence the schemata, associated with the sensor. With a fixed mutation rate for each gene, the number of mutants of a given schema in the population will depend upon the number of copies thereof. Thus by providing many copies within a chromosome, the effective mutation rate is correspondingly increased. As a result, this (hypothetical) mechanism provides many variants relevant to the crisis. At the same time it retains whatever advantage remains to the original schema x. In biology there are varying amounts of evidence for the foregoing responses to nonstationarity, and some of the predicted effects have been demonstrated in simulations, but again we are a long way from a theory, or even good experimental confirmation, of their efficiency. |
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In these nine chapters we have come only a short way in the study of adaptation as a general process. The book's main objective has been to make it plausible that simple mechanisms can generate complex adaptations; however, the book will have fulfilled its role if it has communicated enough of adaptation's inherent fascination to make the reader's effort worthwhile. |
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