Mutation and Molecular Evolution

Abstract

The mutation process provides all the genetic variants from which evolution selects the most useful in order to produce the present-day diversity of living organisms. Until recently, evolution theoreticians have taken mutation more or less for granted, concentrating mainly on the theory of natural selection. The founders of the concept of molecular evolution on the one hand and Kimura (1968) with his theory of neutrality on the other have directed the interest of theoreticians toward mutation again. In view of the considerable amount of experimental work with different species, one would expect that theories in this field should be backed by a very detailed knowledge of the conditions under which mutations occur in nature. Surprisingly, however, this is not the case: most experimental work has been done on mutations which were induced either by ionizing radiation or by chemical compounds. From this type of work, only very limited information can be gained concerning spontaneous mutation. In addition, such research is usually carried out more or less as a sideline of other work. Molecular biology has taught us that the observed mutations, even if they can be traced down to the level of the polypeptide chain, are the end result of a complex interaction of primary events which are under genetic control. We should also consider the primary changes in the DNA, the probability of which depends on metabolic differences, the efficiency of polymerases, etc. How many of these changes will finally become visible as mutations depends on the efficiency of repair processes. However, polymerases, as well as repair processes, are under genetic control (cf. Drake, 1973).