Question

suppose you breed fancy cats and cat fur comes in two types: long or short. You discover that when a purebred long-haired cat and a purebred short-haired cat mate, something unusual occurs: all of the female offspring have patches of long hair and patches of short hair. No two female cat look the same. All of the male offspring have fur length that matches their mother's. Your line of female cats with patchy fur becomes very popular among cat breeders, you continue breeding purebred long-hairs with purebred short-hairs to get the patchy female offspring. After several years and hundreds of kittens, you are to find a cat with a random mix of long and short fur that is male. This is the only patchy male you have seen. What is unusual about the chromosomes of this male cat?

Answer 1

Answer :

When a purebred long-haired cat (say male) and a purebred short-haired cat (say Female) mate, Their offspring are such that all the female kittens have a mix of both phenotypes i.e.. patches of short and long hair. Whereas all male kittens have short hair (hair length similar to their mother). This is only possible when this gene for hair length is X linked and both genes for long hair and short hair are codominantly expressed.

The following is the cross between purebred long-haired cat (say male) and a purebred short-haired cat (say Female) where XL denotes the X chromosome linked with the long hair trait and XS denotes the chromosome with the short hair trait :

After many generations, we find a male cat with patchy hair length. This can only occur when this cat has inherited an extra copy of the X chromosome and hence carries 2 X chromosomes one each coding for long hair and short hair along with the usual Y chromosome. The genotype of this male cat will be XLXSY.