Genetics question regarding mutt birds 😁

[NatJ]

All 8 chicks have light skin even though mom has black. Do the same genetic rules apply to chicks with a melanistic mom (and light skinned dad) that you described for ones with a melanistic dad (and light skinned mom)?

If the father is pure for light skin (Id/Id), then he passes the dominant gene Id to each chick he sires, and they all show light skin.

For a daughter, she has Id on the Z chromosome, and nothing on her W chromosome.
For a son, he has Id on one Z chromosome, and id+ from his mother (allows dark skin) on his other Z chromosome. So he shows light skin, but also carries the gene that allows dark skin.

Based on the outcome with the brahma's chicks, I'd expect the reverse with this clutch...all males being dark skinned and all females light skinned.

That would seem logical, but it's not actually how sexlinked traits work in chickens.

For traits on the Z sex chromosome:
If the father has the recessive trait and the mother has the dominant, you get daughters who match the father and sons who match the mother (but the sons carry the father's trait too, and can pass it to their own sons and daughters.)

If the father has the dominant trait, all chicks show that trait, no matter what trait the mother has. Sons also carry whatever trait the mother has, but daughters do not, because the Z chromosome does not pass from mother to daughter. (W passes from mother to daughter, Z from mother to son and from father to all chicks.)

But I find it hard to believe I got 8 pullets!

I agree that's pretty unlikely, although it's not completely impossible.

I'm thinking the rules might only apply when dad is melanistic and mom is light.

Exactly right.

 

[renk777]

If the father is pure for light skin (Id/Id), then he passes the dominant gene Id to each chick he sires, and they all show light skin.

For a daughter, she has Id on the Z chromosome, and nothing on her W chromosome.
For a son, he has Id on one Z chromosome, and id+ from his mother (allows dark skin) on his other Z chromosome. So he shows light skin, but also carries the gene that allows dark skin.


That would seem logical, but it's not actually how sexlinked traits work in chickens.

For traits on the Z sex chromosome:
If the father has the recessive trait and the mother has the dominant, you get daughters who match the father and sons who match the mother (but the sons carry the father's trait too, and can pass it to their own sons and daughters.)

If the father has the dominant trait, all chicks show that trait, no matter what trait the mother has. Sons also carry whatever trait the mother has, but daughters do not, because the Z chromosome does not pass from mother to daughter. (W passes from mother to daughter, Z from mother to son and from father to all chicks.)


I agree that's pretty unlikely, although it's not completely impossible.


Exactly right.

If the father is pure for light skin (Id/Id), then he passes the dominant gene Id to each chick he sires, and they all show light skin.

For a daughter, she has Id on the Z chromosome, and nothing on her W chromosome.
For a son, he has Id on one Z chromosome, and id+ from his mother (allows dark skin) on his other Z chromosome. So he shows light skin, but also carries the gene that allows dark skin.


That would seem logical, but it's not actually how sexlinked traits work in chickens.

For traits on the Z sex chromosome:
If the father has the recessive trait and the mother has the dominant, you get daughters who match the father and sons who match the mother (but the sons carry the father's trait too, and can pass it to their own sons and daughters.)

If the father has the dominant trait, all chicks show that trait, no matter what trait the mother has. Sons also carry whatever trait the mother has, but daughters do not, because the Z chromosome does not pass from mother to daughter. (W passes from mother to daughter, Z from mother to son and from father to all chicks.)


I agree that's pretty unlikely, although it's not completely impossible.


Exactly right.

I finally got my hands on a genetics book! But I have no time to read tonight. Wondering what the quickest way ton achieve a melanistic calico would be? 2 of the sons are definitely calico. They have room for improvement but I'm happy enough with the amount of white I'm seeing at around 1 month in age. If I understood you right, these boys could carry the genetics to show the black pigmentation even though they themselves do not. If I were to cross the more heavily mottled son back to mom with the black skin, could any offspring have the black skin or would it just be one gender? And which one? My eventual goal is to have melanistic calicos that lay colored eggs. Not set up for this yet but if I hatch some out every couple years, I want to be really careful with which ones until I have more space!

 

[NatJ]

If I understood you right, these boys could carry the genetics to show the black pigmentation even though they themselves do not.

Yes.

If I were to cross the more heavily mottled son back to mom with the black skin, could any offspring have the black skin or would it just be one gender? And which one?

If the mother has dark skin,
and her son has light skin,
then crossing the son back to her should give both skin colors, in both genders.

So you should expect 25% each of:
light-skinned males (they also carry the gene that allows dark skin)
dark-skinned males (pure for the gene that allows dark skin)
dark-skinned females (dark skin on the Z chromosome, nothing on the W chromosome)
light-skinned females (light skin on the Z chromosome, nothing on the W chromosome)

 

[renk777]

Yes.


If the mother has dark skin,
and her son has light skin,
then crossing the son back to her should give both skin colors, in both genders.

So you should expect 25% each of:
light-skinned males (they also carry the gene that allows dark skin)
dark-skinned males (pure for the gene that allows dark skin)
dark-skinned females (dark skin on the Z chromosome, nothing on the W chromosome)
light-skinned females (light skin on the Z chromosome, nothing on the W chromosome)

Perfect! TY!!