‘Grizzled’, a mutant in linkage group X of the mouse

Abstract

Grizzled ( gr ) is a recessive gene with complete penetrance but reduced viability. It is linked with waltzer ( v ) in linkage group X, the recombination frequency being 14·6 ± 2·6%. Its visible effect is to dilute the yellow pigment of the hairs. Body weight is reduced by about 25% atbirth and remains at about 10–20% below that of non-grizzled litter mates. Viability up to the time of classification is about 50–60% of that of non-grizzled litter mates. The mortality of grizzled homo-zygotes occurs at all stages from about 10 days of gestation up to the time of classification. No specific cause of the mortality was evident.