An example of epistasis is pigmentation in mice. The wild-type coat color, agouti
(AA), is dominant to solid-colored fur (aa). However, a separate gene (C) is necessary
for pigment production. A mouse with a recessive c allele at this locus is unable to
produce pigment and is albino regardless of the allele present at locus A (Figure 1).
Therefore, the genotypes AAcc, Aacc, and aacc all produce the same albino phenotype.
A cross between heterozygotes for both genes (AaCc x AaCc) would generate offspring
with a phenotypic ratio of 9 agouti:3 solid color:4 albino (Figure 1). In this case, the C
gene is epistatic to the A gene.
quidditch wrote:I don't think that's normal, how old is it?
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