And only the X chromosome actually carries this color blind gene. And so what that means is only one of the sex chromosomes, namely the X chromosome, will carry that gene. For this particular trait, the Y chromosome doesn't actually carry anything. And that's exactly why this X will get the red lowercase C because the person is color blind, and the Y doesn't actually get anything because the Y chromosome doesn't actually contain that particular gene. Okay, so now we know what the layout is. Now we know what the genotypes of these individuals are.