Why do some mice have multiple genetic mutations within the same strain?
For a variety of reasons, many of the mice with spontaneous mutations contain multiple genetic mutations within the same strain. In some cases this is because a mutation is propagated with the aid of a mutation affecting coat color. In the strain carrying the diabetes mutation, C57BLKS/J-m +/+ Leprdb(Stock No. 000642), Leprdb is maintained in repulsion with the closely linked coat color marker misty, (m). The mating system used produces three genotypes which are phenotypically distinguishable: • + Leprdb/+ Leprdb fat and black • m +/+ Leprdb lean and black • m +/ m + lean and misty (dark grey) An example of multiple mutations carried within the same strain is the JE/Le a/a f/f je/+ ru/ru strain (Stock No. 000259). JE/Le mice are homozygous for nonagouti (a) flexed-tail (f), and ruby-eye (ru) but the strain is maintained heterozygous for the neurological mutation, jerker (je). Most investigators purchase JE/Le mice to study the jerker mutation. The Jackson Laboratory supplies both indiv
