[allmendream]

Yes, there is a difference in what parent gives you the gene sometimes, it is an interesting phenomenon and leads to differences in reciprocal crosses; this has NOTHING to do with sexual determination. The male gives a signal for strong placental growth for both his male and female offspring, so how in the world is it tied to sexual determination?

[AndrewC]

The male gives a signal for strong placental growth for both his male and female offspring, so how in the world is it tied to sexual determination?

Because females do not give that signal. They give the opposite signal. It is tied to the sex of the provider and it is the sex gene that determines sex.