Cryptic mutations: their predicted biochemical basis, frequencies and effects on gene conversion.

Cryptic mutations are undetected base changes in genetic DNA (or hereditary RNA). Some kinds of base change are normally undetected; others may or may not be detected, depending on experimental conditions, procedures and genotypes. Cryptic mutations could affect gene conversion results because when heterozygous they cause mismatched base pairs in hybrid DNA in the same way as known mutations, but the experimenter is unaware of them. Cryptic heterozygosity will usually be much more frequent in heterothallic than homothallic organisms. The effects of cryptic mutation heterozygosity on recombination and conversion of known mutations are predicted with reference to co-conversion, map expansion and polarity. Relevant evidence is considered.