- Thread starter
- #11
- Apr 2, 2015
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It does. Thank you very much. SO much more complicated than I originally thought but I understand now.The barring gene is dominant. It expresses if a bird carries it. Sapphire gem hens do not have barring, and therefore do not have the barring gene.
The reason why crosses with sexlinked genes like the barring gene work to make sexlinked chicks is because hens can only pass sexlinked genes to their sons, never to their daughters. Thus, if you have a barred hen mated by a non-barred rooster, only the resulting male chicks could have inherited the barring gene and the female offspring cannot. The chicks can then be told apart because the male offspring have the barring head spot in their chick down and the females do not. As mentioned by Ridgerunner, there are other genes that might make it hard to see whether there is a head spot or not, but the bare basics of it is that females cannot inherit barring from their mothers, and thus if the mother is the only barred bird in the cross, then only the male chicks will inherit barring.
Now, the other half of the equation is that males can pass sexlinked genes to their offspring of either sex, and they do so equally and without any discrimination. Thus a male that is barred might have both male and female offspring with barring, and so those chicks cannot be sexed by whether or not they inherited the barring gene.
Sapphire gems, as you know, are the result of crossing a non-barred male to a barred female, making barred male sapphire gems and non-barred female sapphire gems that can then be sorted at hatch by that trait. Since sapphire gem males inherit barring, that means they can then pass that barring to their offspring of either sex because males pass on sexlinked genes indiscriminately. So crossing two sapphire gems together will not make more sexlinked chicks. It will simply make blue, black, and splash chicks that may or may not be barred regardless of their sex.
The long and short of it is that sexlinked crosses are generally one-off things. The offspring from such crosses can be sexed at hatch, but as a result of the cross they no longer have the appropriate genes to pass on to their own offspring in order to make more chicks that can be sexed at hatch. I hope that all makes sense!
