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) an autosomal recessive with sex-limited expression. D) an X-linked dominant. E) an autosomal dominant with sex-limited expression.

Question

Quizplus · Accepted Answer

The fact that the spiky fur trait is only present in males suggests that it is sex-limited in its expression. The fact that it is not present in the F1 generation suggests that it is recessive, and the fact that it appears in 1/4 of the F₂ males but in none of the females (who all have soft fur) suggests that it is an autosomal recessive trait with sex-limited expression. Therefore, the best choice is C, an autosomal recessive with sex-limited expression.

Suppose You Discover a New Variant in Which Mice Have