The Spontaneous Mutation Rate Revisited and the Possible Principle of Polymorphism Generating More Polymorphism

T h e molecular requirement to be a gene (a master of inheritance) is very exact. Unless affected by a mutation, each inherited trait perpetuates itself through many, many generations of individuals. T h e n~olecule which is a gene must have a unique property, so that the exact replica of itself can be made before each ccll division. W e now know that because of thc inherent complementality that exists between the two pairs of bases, adenine and thymine as well as guanine and cytosine, in replication each uncoupled strand of the D N A double helix can serve as a template for recreating a missing strand complementary to itself. Indeed, D N A is the master of inheritance, and, in reality, each structural genc is a stretch of base sequence which comprises a part of the D N A strand. Although D N A replicates in an extremelv conservative manner, mistakes do occur and rcsult in changes in the base sequence of a cistron. Since evolution is the consequence of gcnetic changcs and not of conservation, the accurate estimation of the spontaneous mutation rate is of the utmost importance in understanding evolution.