For a more practical example, how does this work for the daughter of a colorblind person (the colorblindness gene is on the X chromosome)? Do they have four types of cones?
Yes, but it's not limited to that case - there's two common variants of the green cone that respond to different wavelengths and people with two X chromosomes can have both, improving colour identification.
I'm kind of late to this but for some context - bonzini knows me from a long time ago when I was still a genetics student and the joke here is that given where I am now in my career I still get to occasionally answer questions based on that background
