Help me with sexing a chick using genetics.

[chickgirlz]

I read in my chicken raising guide that the rooster passes his genes to the female chicks and the hen passes hers onto the male chicks. I have a chick with an Auracauna rooster dad and unknown hen as a mother. The egg was spotted and brown (so the mom wasn't an Auracauna as the egg wasn't blue) and the chicks legs are grey (an Auracauna trait), so I am thinking it is a female. Am I correct, or is there more to it than that? Thanks to anyone who can help!
And sorry for no photo...the chick is only 1 week old so there's not much to see as far as combs and feathers go.

 

[itom37]

There is much more to it.

Similar to the X and Y chromosomes in humans, birds have a W and Z chromosome. Rather, females have a W and a Z, males have two Z's. Each bird will pass one of these on to the offspring. A male must pass on a Z, the female can pass on a W or a Z. The situation is opposite in humans where the male can pass on an X or a Y, thus it is the makeup of the male gamete that determines sex of the offspring. In chickens, the female passes on the "deciding factor": a Z (male) or a W (female).

Unless you know specific traits coded by the Z and W chromosomes (such is probably the case for down pigmentation at birth in sex links chickens), you can't arrive at a sex determination based on a characteristic like this. If you could... it would already be being exploited as with the sex links.

 

[itom37]

To clarify a little more: the leg color of the chick probably is a trait derived from the father, however there is no indication that that trait is coded by one of the sex chromosomes. Much like a father could have both a son and a daughter that bear his characteristics.

A simple situation in which your idea would work would be if 1) Green legs were a trait coded by the W chromosome, 2) The mother of the chick bore this trait (remember females carry the W chromosome), and 3) the chick had green legs, 4) the trait is simple, and other more complex mechanisms of gene regulation are not at play). You would then be right to think you're looking at a female chick.