Ya, I'm just wondering why there is no barring.
On which one? The rooster or the chick?
The rooster has no barring because he just does not have the barring gene.
I'm pretty confident that the chick does have the barring gene (because he has the light head spot), but he does not yet have enough feathers to look barred. That will happen as he grows.
I could be wrong, but I've heard females can sometimes have a small spot, and males a larger one. I'm definitely not an expert in the subject though.
It depends on whether you are dealing with purebreds of a barred breed (like Barred Rocks) or a cross of barred x not-barred (which is what you have.)
Barred Rocks have headspots on males and females (bigger ones on males, smaller ones on females.) But for sex-linked crosses like you have, the males have head spots (any size) and the females do not.
The genetics involved:
The barring gene is incompletely dominant. A male with one barring gene will have a smaller head spot than a male with two barring genes. A male with two barring genes will grow up to have an overall lighter color (more white/less black) than a male with one barring gene.
Because barring is on the Z sex chromosome, a female can never have more than one barring gene. She has chromosomes ZW, while a male has ZZ.
In the breeds that are pure for barring, the males have two barring genes (on their two Z chromosomes), and the females have one. That means the females have the smaller head spot and overall darker color, while the males have the larger head spot and overall lighter color.
But in mixed-breed chicks, it can go several ways:
--a barred hen with an unbarred rooster will produce chicks where only the males have barring (one barring gene) and the females have none at all. This is because the mother gives her Z chromosome (with barring) to her sons, and her W chromosome to her daughters (makes them female, but does not have barring.) This is what your cross is.
--a rooster with two barring genes, mated with an unbarred hen, will produce sons and daughters that each have one barring gene (he gives a Z chromosome, with barring, to every chick.) These chicks cannot be sexed by looking for barring or not-barred, because they are all alike with one barring gene each.
--a rooster with one barring gene, mated with an unbarred hen, will give the barring to half of his chicks (half of males and half of females), and will give non-barring to the other half of his chicks (half of males and half of females.) His chicks are not color-sexable either.
--a rooster with one barring gene will give the barring to half of his chicks and not to the other half. If he is mated with a hen who is barred, that means some sons will have two barring genes (one from each parent) and some sons will have just one barring gene (from the mother.) The daughters all get a W chromosome from the mother, but they may get barring or no-barring from the father. So there will be some daughters with no barring (easy to recognize), some sons with two barring genes (somewhat easy to recognize) and lots of chicks with one barring gene (some males and some females, with no chance of sexing these ones by color.)
