Chapter 3, Problem 31P

While examining a young tortoiseshell cat, you and the veterinarian you are interning with get a surprise $\text{-}$ the cat is male, not female $\text{!}$ from your undergraduate genetics course, you recall that tortoiseshell coats are produced by the random X $\text{-}$ inactivation that takes place in mammalian females. The veterinarian orders a chromosome analysis of the cat and finds that he is $\text{XXX : He}$ has two X chromosomes and one Y chromosome. Help the veterinarian figure out how a tortoiseshell cat could be male. (Hint $\text{:}$ Think about X $\text{-}$ inactivation in mammals with two X chromosomes.)