Understanding egg color genetics

DarJones

Songster
Jan 24, 2021
219
623
113
Pea comb is one of those genes that can be beneficial in some cases, but in others is undesirable. I wanted rose comb blue egg laying Silver Laced Wyandottes. To get that combination, I had to have the gene for straight comb on chromosome 1. The gene combination of straight comb on chromosome 1 plus the rose comb inversion on chromosome 7 is what produces rose comb phenotype.

Pea comb is a variant of the single comb gene on chromosome 1. It is approximately 80 centimorgans (not yet proven) from the oocyanin gene that produces blue eggs. At that distance, approximately 1 in 1000 chicks would get a crossover which would re-link oocyanin from pea comb to single comb.

Cream Legbars are one breed in which the pea comb linkage has been broken. There is a line of whiting blues that have straight comb. Silverudd blues have straight comb. The blue egg laying brown leghorns developed at UARK have straight combs. To the best of my knowledge, these are the only currently available blue egg layers that have straight comb.
 

ALWAZL8

Chirping
Apr 26, 2019
13
35
54
Monroe, LA
Yes, if the chicks inherit the blue egg gene from their father.
You need one that has the blue egg gene, so it sounds like the fibro egger is your best bet.
Yes, he would be the only one of my 3 roos that I know has a blue egg gene. Olive egger is only a maybe, but it would be waaaay back somewhere. He's an F5 or F6 olive egger.
When people say the pea comb gene is linked to the blue egg gene, that is not quite accurate. It's more that pea-or-not is linked to blue-or-not. The genes are close together on one of the chromosomes, so they usually get inherited together.

Examples of each possible combination:
Ameraucanas have pea comb, blue egg
Cream Legbars have not-pea comb, blue egg
Brahmas have pea comb, not-blue egg
Marans have not-pea comb, not-blue egg

So pea comb can help you track the blue egg gene when you are working with Ameraucanas, but not with your CCLB (Crested Cream Legbars) because they have the blue egg gene linked to not-pea comb (single.)

Easter Eggers and Olive Eggers can be either way, depending on what breeds they got their blue egg gene from, but the pea comb/blue egg link is pretty common among them. Although I have seen some pictures of Olive Eggers that were Legbar/Welsummer crosses, with single combs.
Makes sense. My olive egger pullet came from my blue Ameraucana hen and BCM roo. I would see a single comb in any chicks from a mating of my CCLB and BCM roo I would imagine since both parents have single combs so that makes sense, too.
 

Starbawk

Songster
5 Years
Mar 28, 2017
78
91
121
If one copy of the blue egg gene is present, then all eggs will be blue. Two copies may get slightly more intense blue color, but is otherwise indistinguishable. If there are no blue genes, then the base color white will be expressed.

Brown eggs are caused by porphyrin which is deposited as a coating on top of the white or blue egg.

What about green eggs? Green is from expression of the porphryin biopath on top of the blue egg gene on top of the white eggshell base color. Varying levels of green can be produced based on modifier genes in the porphyrin biopath.
So would it be possible to breed one or more birds that have two copies of the blue egg gene with brown overlay, in order to breed a true breeding green-egg laying line of birds?
 

DarJones

Songster
Jan 24, 2021
219
623
113
As many Ameraucana breeders have found, it is very difficult to turn off the porphyrin coating once it is turned on. Yes, you can breed an olive egger fairly easily. However, if the zinc white gene is present, the eggs will be tan tinted instead of brown over blue.
 

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