Understanding egg color genetics

[DarJones]

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]

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.

 

[NatJ]

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.

Yes, that is right: single comb is recessive, so two single comb chickens will produce single comb chicks.

 

[Starbawk]

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?

 

[nicalandia]

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?

Yes, as they are not mutually exclusive

 

[DarJones]

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.

 

[SourRoses]

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.

I've been using this very helpful thread as a guide in my big project.

Because of it, I started a side project to get zinc white (leghorn) introduced.
Those F1 cross birds are about to come into lay; I kept one of their brothers too. I'm hoping that breeding the siblings together will "set" the zinc white gene.

The F2's I'll cross back to the same brown egg breed; then breed those siblings together. As many times as it takes until they lay clean white and look like my brown egg breed. But not to SOP, just to help my main project.

I suppose I'm still wondering about the tan tint. How difficult will it be to clean up that last little bit of brown?

 

[KitchenFamilyFarm]

So what happens when you cross a White Leghorn male with an existing flock of colored egg hens.
Will the offspring breed true to the existing egg color?

 

[R2elk]

So what happens when you cross a White Leghorn male with an existing flock of colored egg hens.
Will the offspring breed true to the existing egg color?

It depends on whether the hens are heterozygous or homozygous for their egg colors. Not a simple yes or no answer.

 

[NatJ]

So what happens when you cross a White Leghorn male with an existing flock of colored egg hens.
Will the offspring breed true to the existing egg color?

Breed true, not really, if you mean for multiple generations.
In the first generation, you should get at least some that lay blue or green eggs, but you might get some that lay white or brown.

For each hen that has one blue egg gene and one not-blue egg gene, she will give the blue egg gene to about half of her chicks, and the not-blue egg gene to the other half of her chicks. Since all the chicks inherit a not-blue egg gene from the Leghorn father, half of the daughters will lay blue or green eggs, while the other half lay white or brown eggs.

For each hen that has two blue egg genes, each of her chicks will get one blue egg gene from her, and one not-blue egg gene from the Leghorn father. Every one of those daughters will lay colored eggs (blue or green). But when those daughters grow up, if you breed them, they give the blue egg gene to half of their chicks, and the not-blue egg gene to the other half of their chicks (same situation I described in the previous paragraph.)