The genes for hair color in mice is being studied. This is what is known: the ge

Question

The genes for hair color in mice is being studied. This is what is known: the gene for hair color is the "Q" gene ("Q" allele leads to brown hair color and the recessive "q" allele leads to green hair color). There is a mutation in another gene which produces stripes. Some of the mice have solid hair color, but others have a striped phenotype with white striped patterns. It is simple to produce a purebreeding progeny of either brown or green, but is impossible to produce a progeny of purebreeding stripped mice. Stripped mice which you know is Q/Q when interbred always yields some solid brown and some pure white mice as well as striped ones. This is also the case of stripped orange mice too; when interbred, they produce some solid white, solid green, and stripped green progeny. The gene that is observed is named ST for stripped.

1. Explain how the ST gene affects hair color. This must explain the results from above.
In addition, you decide to interbred two dihybrid mice (genotype: Q/q; ST/st), give the expected phenotypic and genotypic ratio of the F1 progeny.

Explanation / Answer

The presence of a single mutant allele (STst) causes the stripes, whereas (STST) is normal coloration, and (stst) produces solid white. The reason it is impossible to produce a purebreeding striped lineage is that it requires a heterozygous genotype and a cross between two heterozygotes will always result in a 1:2:1 genotypic ratio

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