Question about comb genetics

If walnut combs are similar to rose combs than you would still have to watch the offspring. In rose combs - Rose combs are dominant. R while single combs are recessive r.

An R/R bird bred to a r/r bird will result in R/r. Bird shows rose comb, but is hiding a recessive single comb gene (50%).

Breed this R/r bird back to an R/R bird and you birds will still be rose comb birds but (25%) will still be R/r.

You could just breed your crossed birds back to a r/r bird and hatch out some eggs if all hatchings show the walnut then it is carrying a recessive single comb gene. if all hatching are walnut it is carrying both walnut genes and I would breed this bird going further and test for other birds that breed pure also.

I do believe if I read it correctly walnut is a dominant as well over single comb.

Check out this link it may help as well.


https://www.backyardchickens.com/a/comb-genetics

 

Not exactly, but eventually. It seems to be a little more complicated than that.

I consider a walnut and a cushion to be basically the same because it seems that it's just enhancers or modifiers that account for the difference in shape. (supposed to be P/P R/R or something like that to be "Pure." P=Pea, R=Rose) But, yes, I do understand that some breeds are specifically supposed to have a walnut and some are specifically supposed to have a strawberry. In those cases, it's not the same thing to me.

What's been happening for me is that when I cross a "pure" walnut or a "pure" cushion with a "pure" single comb is that I very often get another cushion or walnut.

But when I take that next generation and successive generations and cross again with a single comb, I will sometimes get a bigger pea comb with funny rose comb protuberances on it. I can sometimes get a cushion, but not very often. When I breed that funny comb with another non-pure cushion, I can get a decent cushion or walnut, but I can also get something a little more like a walnut with a spike like on a rose comb or just about anything in between that looks like a big or normal sized pea, rose, or walnut/cushion.

If I breed my cushion offspring (second generations) back to a "pure" parent or aunt/uncle, I will get some decent cushions, but I still will also get rose and pea comb conglomerations of differing sizes. The decent cushions are not likely going to be R/R, P/P even though they will often show up as a cushion. Their brothers and sisters will often have variations of pea combs and rose combs.

You may get larger wattles also when you breed in a single combed chicken. (Usually walnut combed chickens have smaller wattles.)

There are modifiers and enhancers, etc., in comb genetics that aren't well understood yet--not just by me, but by real genetic experts. I've also heard talk of "incomplete dominance," which sounds like a good explanation. Trial and error is the way to get the type of comb you want, if you want something specific. I don't think this is a test mating issue because it's really not something firm that you can plan for very well because of the modifiers and enhancers, etc., which I don't think are specifically identified yet. I believe crests can further complicate the issue also.

So walnut combs may be dominant over single combs, but it's not dominant in the same way an E/E black chicken being bred to a red chicken (eb/eb) where all the chicks (offspring) will almost assuredly be black because E/E is dominant over (eb/eb).

 

Spangled is correct. Cushion/walnut comb is a combination of Rose Comb and Pea Comb. Another good thread on combs here.

https://www.backyardchickens.com/t/606259/comb-genetics