Cats normally have a total of 18 toes, 5 on each front paw and 4 on each back paw. But some cats express the dominant phenotype for polydactyly, which results in the development of extra toes on one or more paws. Jake, a Canadian tabby cat, has 28 toes and is recognized by the Guinness Book of World Records as the cat with the most toes.
Suppose that Jake mates with a female cat, Lucy, who has 18 total toes. Over several years, they have multiple litters and a total of 16 kittens (10 males and 6 females). The total number of toes on each kitten ranges from 21 to 25.
-Along with having a variable number of toes, some kittens from Jake and Lucy's litter had a white spot on their nose. In fact, out of the 16 kittens, all 10 males had the white spot, but none of the 6 females had the white spot. Jake has a white spot on his nose, but Lucy does not. What can you conclude from this information?
A) A sex-linked gene that controls the expression of the white spot is found on the Y chromosome.
B) A sex-linked gene that controls the expression of the white spot is found on the X chromosome.
C) The genes for the white spot and for polydactyly are linked.
D) The genes for the white spot and for polydactyly are not linked.

Question

Quizplus · Accepted Answer

Since all the male kittens have the white spot on their nose and none of the females do, it suggests that the gene controlling the trait is linked to the X chromosome. This means that the gene is sex-linked and inherited differently in males and females, with males only inheriting one copy of the X chromosome.

Cats Normally Have a Total of 18 Toes, 5 on Each