[Mr. K]

If a person has an X and Y chromosome, he is male. How hard is this?

You can dress up a pig and call it a sheep, but it is still a pig.

[agere_contra]

If a person has an X and Y chromosome, he is male.

I forget the exact fraction but about 1 in 20 woman are XY, believe it or not. Basically the Y chromosome is not the sole sex-determinant. XY women are testerone-insensitive, and are more feminine than XX women.