Question

Having 2 X chromosomes (ie XXY) can cause a male cat to be tortoise shell or calico, is the same possible in humans?

Answer 1

Though phenotype of XXY human is male, the person is sterile and suffers from Klinefelter's syndrome.

Explanation:

In human, XXY is a chromosomal abnormality: it is trisomy of sex chromosomes: a condition of 2n+1 (there are 47 chromosomes in cells rather than the normal 23 pair/46). Although sterile, presence of Y chromosome creates male appearance.

"No matter how many additional X chromosomes are present, and as many as four have been observed, the presence of a single Y chromosome is sufficient to shift development toward masculinity"- Strickberger. This is because genes triggering development of testes are located on Y chromosome.