Breeding out a recessive trait?

[ravenridgechick]

Hi, I grew out some nice birds last summer, only they carry yellow skin and the breed is supposed to have white skin and slate legs. I was planning to mate the hens with a cock with white skin and slate legs from my own flock, and only keep the daughters to mate back to him. Is this the most efficient way to breed the yellow skin gene out? Or is there a better route I should be taking? Thanks, any advise or help is appreciated. -- RRC

 

[junebuggena]

Sounds like a good plan to me. Then, you can take the offspring from the daughters bred to the father and test breed with a yellow skinned cock. If you only get white skinned chicks, then you know you've successfully bred out the yellow skin gene.

 

[ravenridgechick]

Thank you. It's good to know I'm on the right track.

I should mention the hens look like they have slate legs, but the pads of their feet show a slight willow cast, as did their legs when they were chicks.

If I only keep daughters and grand daughters from the white skinned slate legged cock, is test mating future offspring even necessary? Currently, I don't keep any breeds with yellow skin.

 

[venymae]

Thank you. It's good to know I'm on the right track.

I should mention the hens look like they have slate legs, but the pads of their feet show a slight willow cast, as did their legs when they were chicks.

If I only keep daughters and grand daughters from the white skinned slate legged cock, is test mating future offspring even necessary? Currently, I don't keep any breeds with yellow skin.

Yes, because the recessive yellow gene (lets call it 'y') can hide for MANY generations. You need to test the birds with another recessive carrier that is 'yy', if they carry both the white dominant genes 'WW' (we are assuming Mendelian genetics here!) there will be no yellow offspring, if they only carry one (Wy)there will be some yellow and some white in the offspring. If you didn't test breed them and simply bred them to a dominant 'WW' bird then the offspring could hide the recessive trait for a long time and you would never know, until it was bred with another bird that accidentally carried a recessive gene too.

 

[ravenridgechick]

^ Thank you! It appears test mating is the only sure fire way to know if yellow skin has been bred out of future generations. So much for short cuts, or an easy project! lol I guess I had it in my head yellow skin was recessive AND sex-linked, but unfortunately that is not the case. Unwanted recessive genes are a real pain.

 

[Fairview01]

It's not that easy. A recessive trait can be carried for decades before it shows up again. Assuming white is dominant and represented by an upper case W and yellow is recessive and represented by lower case w, white legged chickens can have either WW or Ww and still show a phenotype of white legs.

If you breed two white legged chickens that are WW and Ww all off spring will have a phenotype displaying white legs but the Punnet square will says 2 will carry the yellow gene but not be expressed.

If you breed a Ww with a Ww probability says one will be WW, 2 will be Ww and one will be ww. Out of four possibilities three will be white legged but 2 will carry the yellow recessive gene.

But these results are theoretical. In the real world each egg fertilized is an independent event. It only averages out in the long run.

If you know your rooster is for sure carrying both dominant genes than to determine which stock to use from the F1 generation many eggs will need to be hatched from a white legged hen and a yellow legged rooster to see if any resulting chicks hatch with yellow legs which will tell you if the hen is carrying the recessive yellow gene being covered by the dominant white gene.

It's reads easier than it is. Good luck.

 

[ravenridgechick]

^ Thanks. Honestly, the fact that recessive traits can be carried, and remain hidden, for decades is really making me consider going forward with this project. I'm beginning to think I'm crazy for even considering it. Test breeding everyone sounds like a lot of work too. I'm not sure the birds are worth the time and effort, tbh. Thanks again. You've given me lots to think about anyway.