In the previous hatching round we began getting baby chicks with black combs and gypsy-face in our Black Barred line. Those pullets are now well into lay and their babies are hatching now. In our present hatch we have 12 of these babies with black combs and faces.
I meant to say that a sex-linked trait could account for our chick statistics if the trait were recessive, the sire is heterozygous (and therefore does not express the trait) and the dams don't have the gene at all, then only daughters of the mating would have the trait in their phenotype, there would be females without the trait and there would be no males having the trait.
I received a line of Black Minorcas from Murray McMurray that had black combs at hatch, but they had a typical Mediterranean comb and face type as adults. Id and barring could be two genes on the Z chromosome that might influence gypsy face, but I don't think the phenotype is sex-linked. Sumatra breeders would have figured that out by now, but maybe not. To determine it all you have to do is the reciprocal crosses and observe the difference between the female progeny of the two different crosses.
TY, rokimoto. It isn't likely that knowledgable people would miss such a simple point. We're not sure that our black-face birds are the same as gypsy-face or mulberry-face, but probably they are. Now, we have enough for the next go-round to do some breeding experiments....
In this statistically (too) small sample, the black comb correlates perfectly with comb size in the chick. The black-comb chicks all have obviously smaller combs than their hatchmates. (They are a single-comb variety.) If the comb size correlates with sex, then the black-comb babies are females.
I don't have enough information yet to even make an intelligent speculation of whether this black-comb trait could be sex-linked. It appeared suddenly in our Black Barred line and we just weren't paying attention to any such trait so our records are blanck until then. But, just because only the females have it isn't enough information to declare the trait to be sex-linked. Males get sex-linked traits too (sex-linked barring, silver, Id and so on)
If the gene for the trait is recessive and on the Z chromosome (i.e. sex-linked) and only the sire has it, then the only chicks in which the trait will express are females. There will be other females without the trait, but no males. This model doesn't fit our data because we know the dams have the trait.
This black-comb trait may be sex-influenced rather than sex-linked, in that the expression of a sex-influenced trait is sensitive to sex hormones of the animal and expresses to a greater degree in one sex or the other.
Well, it's too early for us to know anything reliable from the information we have in-hand.
Rokimoto posted that he had had a black-comb chick. I was wondering if that chick was a pullet or cockerel?
By Anonymous on Saturday, November 17, 2001 - 08:40 pm:
But, this model doesn't fit our data because we know the mothers have the black-comb trait.
If the trait is sex-linked and recessive and the dams have it but the sire does not have the gene, then none of the F1 chicks will display the trait, although there will be male heterozygotes.
If the trait is sex-linked and recessive, the dams have it and the sire is heterozygous (and not expressing), there will be both male and female F1 chicks with the trait.
By Rokimoto on Sunday, November 18, 2001 - 04:36 pm:
By Anonymous on Monday, November 19, 2001 - 04:14 pm: