Suppose you discover a new variant in which mice have spiky fur instead of the usual soft fur.You notice that this trait seems only to be present in males.To investigate this pattern, you cross a spiky-fur male with a soft-fur female, and find that all of the F₁ progeny of both sexes have soft fur.You then interbreed the F₁ and observe that all of the F₂ females have soft fur, but 1/4 of the F₂ males have spiky fur.You conclude that the spiky allele is A)an X-linked recessive. B)Y-linked. C)autosomal recessive with sex-limited expression. D)an X-linked dominant. E)an autosomal dominant with sex-limited expression.

Question

Quizplus · Accepted Answer

The pattern of inheritance observed suggests that the spiky fur trait is autosomal recessive with sex-limited expression, meaning that the allele is located on an autosomal chromosome but its expression is influenced by sex hormones or other sex-specific factors. The fact that only males exhibit the spiky fur trait indicates that the allele is expressed only in the presence of male hormones or other factors specific to males. The 1:1 ratio of spiky:soft-fur males in the F₂ generation is consistent with a recessive trait that is carried on the X chromosome, as males inherit only one X chromosome from their mother and thus have no backup copy of the gene if it is defective. However, this is ruled out by the fact that all the females in the same generation have soft fur, indicating that they inherit a dominant allele from either parent that masks the expression of the spiky allele. Therefore, the most likely explanation is that the spiky allele is autosomal recessive with sex-limited expression.

Suppose You Discover a New Variant in Which Mice Have