Predictability of mutant sequences. Relationships between mutational mechanisms and mutant specificity.

Spontaneous mutations are rare and are produced by multiple biochemical mechanisms. Nonetheless, studies of these mechanisms have revealed striking examples in which mutational specificity can be regularly related to a characteristic of the surrounding DNA sequence and/or the enzymes participating in mutagenesis. Thus, to an increasing degree the DNA sequences of mutants are "predictable." This report considers some examples of predictable sequence changes, evidence for their contribution to mutagenesis in populations, and how the predictability of mutant sequences may be useful to improve our interpretation of the molecular course of evolution from DNA sequence comparisons.