Blue cuckoo Polish

[Turtle1626]

Anyone know what the outcome would be if I crossed to blue cuckoo polish?? Would I get BBS offspring? Or would I just get blue cuckoos?

 

[pipdzipdnreadytogo]

Two blue cuckoos bred together should make about 25% plain (black) cuckoo, 50% blue cuckoo, and 25% splash cuckoo offspring, assuming both are pure for the barring gene.

 

[EggSighted4Life]

assuming both are pure for the barring gene.

Please explain how a barred bird could not be pure for barring if it's visible? Thank you!

While you're at it can you describe the difference between single and double barring genetically speaking rather than just (or in addition to) the visual effect?

 

[pipdzipdnreadytogo]

The barring gene is sexlinked, meaning it resides only on the Z chromosome of the sex chromosome pair. Because birds use the ZW system where males have the matching ZZ and females have the mismatched ZW, females can only either be barred (B/-) or not barred (b+/-). The dash in both of those cases represents the W chromosome where the barring gene just does not exist, whereas the B or b+ is representing her Z chromosome where the gene exists.

Males, because they have two Z chromosomes, can either be not barred (b+/b+), single-factor barred (B/b+), or double factor barred (B/B). Because it's a dominant gene, a male that is single-factor barred (B/b+) is still barred, but has a gene for no barring, b+, that he can pass on. In other words, he's not pure for the gene. In such cases, when crossed to a barred female, his sons will still be barred, always inheriting it from the mother because she only has that to pass on to her sons, but some of his daughters may not be. This is because they inherit the W chromosome from their mother, which does not have the barring gene as mentioned, and have an equal chance of inheriting a Z chromosome with B or b+ from their father. So, if the male is not pure for the barring gene, then some of his daughters may not inherit it and in this case would then just be blue, black, or splash.

As far as the difference between single and double factor barring functionally, the gene seems to have some sort of cumulative effect. I don't know if that's the right wording for it, but I'll explain what I mean. My understanding is that the barring gene works by intermittently shutting off the deposition of pigment in the feather as it grows. This causes intermittent sections of white in the feathers, which visually look like barring. With one copy of the gene, the amount of time that the deposition of pigment is shut off is shorter. With two copies of the gene, it's shut off longer. Hence, double-factor barring being lighter with wider white bars than single-factor barring.

I hope that adequately explains it, but if not let me know!