Rose Comb Rhode Island Whites

[rjohns39]

Got a dumb question for you genetics experts... One of my Rhode Island Whites turned out to be a single comb bird. The rest are all rose comb. Is the single comb a recessive gene? My selected birds for breeding are all rose comb and are the best of my flock, do I need to watch for more single combs?

 

[Sneebsey]

Yes, two or more members of your flock only have a single copy for Rose-comb; at least one cockerel and one hen. As Rose is dominant over single comb (wildtype), it will be difficult to tell who without test-breeding to single combed birds.

 

[rjohns39]

Thank you.

 

[nicalandia]

Got a dumb question for you genetics experts... One of my Rhode Island Whites turned out to be a single comb bird. The rest are all rose comb. Is the single comb a recessive gene? My selected birds for breeding are all rose comb and are the best of my flock, do I need to watch for more single combs?

Rose comb is one of the few "Completely Dominant" genes on the chicken genome(phenotype wise) a heterozygous rose comb R/r+ bird will look indistinguishable from R/R birds, this happens on the Wyandotte breed also, from time to time a single comb bird will pop up seemingly out of nowhere, Heterozygous R/r+ males are more fertile than R/R males and this will give them a better chance of passing their genes

 

[nicalandia]

http://www.rosecombs.com/documents/low_fertility.pdf?page_id=116
Homozygotes (RR) and heterozygotes (Rr) are phenotypically indistinguishable and can only be differentiated by using breeding tests. (A homozygous male bred to a single comb female would produce all rose comb offspring. A heterozygous rose comb male bred to a single comb female would produce some rose and some single comb offspring (Crawford and Smyth 1964a).

Average fertility of RR males was significantly lower than the fertility of males of the other genotypes. The average fertility for heterozygotes and single comb males was almost the same (Crawford and Smyth 1964a).

 

[rjohns39]

So breeding a rose comb male to a rose come female, regardless of (RR or Rr) should produce rose comb offspring? And I should expect a lower hatch rate?

Thanks. That was a good read...

 

[nicalandia]

So breeding a rose comb male to a rose come female, regardless of (RR or Rr) should produce rose comb offspring? And I should expect a lower hatch rate?

Thanks. That was a good read...

R/r+ rooster crossed to a R/r+ female will produce 25% r+/r+(single comb), 25% R/R(homozygous rose comb) and 50% R/r+ progeny of both genders, it's impossible to distinguish R/r+ from R/R males, unless you cross it to a single comb hen and see the result of the cross(50% r+/r+)

R/R males have lower fertility than R/r+ males, R/R females have no issues at all, the issue seems to be sperm motility, the reason why r+/r+ birds keep popping up is due to breeders intentionally keeping known R/r+ males or a few r+/r+ males to keep up with fertility, also positive breeding pressure as on a large flock R/r+ males will produce considerable more progeny than R/R males.

 

[rjohns39]

It kind of scares me that I actually understood that. My last genetics lesson was on turkey colors.... Thanks for all the info.

 

[HuffleClaw]

Just thread stalking


Thanks for posting! Interesting

 

[TomNY]

Test mating is not easy because there are four comb genes. Rr rr,rR rr,rr Rr or rr rR will still give you a rose comb. A single comb is rr rr.