Natural mutation rates in the house mouse: plan of study and preliminary estimates.

Abstract

Abstract From the autumn of 1963 to the summer of 1964, 630320 mice in 18 inbred strains and 173754 mice in six F 1 hybrid generations, produced under regular laboratory conditions, were examined for presumptive natural mutations at any one of five specific coat color loci and at any other locus as well. Altogether 40 of 303 presumptive mutations have proved to be mutations. The preliminary estimates of reverse (recessive to dominant) mutation rates are: 6.5·10 −6 for nonagouti ( a ) to alleles a t adn A w ; 3.6·10 −6 for dilution ( d ) to wild type ( d + ); o for the brown ( b ), albino ( c ), and leaden ( ln ) loci. The preliminary estimates of forward (dominant to recessive) mutation rates range up to 30·10 −6 for the ln locus. Other estimates are 1.1·10 −6 for the tabby ( Ta ) locus and 4.9·.10 −6 for the dominant spotting ( W ) locus. The occurrence of gonadal mosaics may eventually be a means of studying the mutability of genes in cells at all stages of development.