Cat breeders are aware that kittens expressing the X-linked calico coat pattern

Question

Cat breeders are aware that kittens expressing the X-linked calico coat pattern and tortoiseshell pattern are almost invariably females.

Which one of the following statements supports this conclusion?

a)Since females normally have two X chromosomes, random X inactivation during development of a heterozygous female will create a mottled pattern.
Normal males are not mottled, because they only have one X chromosome and therefore can only express one of the two potential X-linked alleles. b)Since males normally have one X and one Y chromosome, random X inactivation during development of a male will create a mottled pattern.
Normal females are mottled, because they have two X chromosomes. c)Since females normally have two X chromosomes, expression of both potential X-linked alleles at the same time in all cells will create a mottled pattern.
Normal males are not mottled, because they only have one X chromosome and therefore can only express one of the two potential X-linked alleles. d)Since females normally have two X chromosomes, random X inactivation during development of a homozygous female will create a mottled pattern.  
Normal males are not mottled, because they are heterozygous and therefore express each one of the two potential X-linked alleles.

Explanation / Answer

a)Since females normally have two X chromosomes, random X inactivation during development of a heterozygous female will create a mottled pattern.
Normal males are not mottled, because they only have one X chromosome and therefore can only express one of the two potential X-linked alleles.

100% sure correct answer

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