Sex linked recessive traits and female avian heritability

[Susan Skylark]

I’m used to mammalian genes, so this whole bird sex genes (female birds have two different chromosomes vs males have it in mammals) thing still seems backwards. I’ve started breeding quail but this question is relevant to any avian sex linked recessive trait so hang in there you turkey or pigeon enthusiasts! In quail the roux gene is sex linked recessive, a hen needs one copy and a male needs two to express it. I have two hens with the gene but no males that carry it. Doing the math as it were, my hens will never pass the gene on to their daughters, correct? The gene is on the chromosome that the male has two of but the female only has one copy (sorry don’t know the correct nomenclature, XY in mammals). The hen has a fifty percent chance of passing it on to a son but she will always pass the non-affected chromosome to her daughters as that is what makes them female, at least if I’m thinking this through correctly? So my only chance of perpetuating this gene is to keep back a few roosters from these hens and see if they throw roux daughters? Or buy some eggs from a roux line! Just want to check my understanding here, thanks!

 

[Susan Skylark]

I’m answering my own question here just in case anybody has a similar question in future. Apparently the Z chromosome is the main sex chromosome in birds, males having two copies, females one Z plus (?) a w chromosome with very little to nothing on it. So a sex linked recessive gene is only expressed on the Z chromosome and a female will always express it, but the male must have 2 copies to do so. When the cells are dividing in the follicle to produce the egg cell (not the actual egg!) the chromosomes divide right down the center and the resulting gamete has either a Z and will be male or a w chromosome and will be female. Thus a female carrying a sex linked recessive gene will throw females that don’t carry the gene and sons that do!