Egg genetics help: Green x white egg results

fatcatx

Songster
8 Years
Apr 7, 2013
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Northern California
I recently got hatching eggs and the person tossed in some bonuses that are an Andulusian x Isbar cross. Presuming the Isbar is a true green egg layer, what color eggs are The hens likely to lay? Very light green? I'm assuming white, brown, and green are all possibilities. Guessing blue is possible but unlikely?

The Isbar really throws me because they are supposed to breed true for moss green eggs if they are good quality; but if you need both brown and blue genes to get green, how can they breed true for green? The brown would have to resurface constantly, right?

Also, can anyone point me to a good resource that explains egg color genetics, what's dominate/recessive, etc.? then I can stop posting these questions. :D I found some very basic ones, but they don't really answer my questions completely.
 
First let me explain what science knows about egg color. 😉
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Blue seems to be controlled by one incompletely dominant gene, O, for the pigment Oocyanine that causes the blue color.

Oo will result in pale blue eggs
OO will result in a more rich blue

Brown in more complicated and is controlled by a network of genes, but it is thought a recessive sex-linked gene, pr, restricts brown pigment.

PrPr would not restrict brown pigment, so eggs would be tinted or brown.
prpr would restrict brown pigment and eggs would have no brown pigmentation.

Creating a chicken that breeds true for green eggs isn't that hard. You just have to fix two genes, if all hens and roosters express OO and PrPr, both brown and blue pigment will always be present in 100% of the offspring.
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So when you cross an Isbar and an Andalusian you could get all colors in the spectrum.

I would expect most of them to be some variant of green as the Andalusian is going to bring prpr, white eggs, to the table, and some unknown degree of hidden brown pigment genes. Blue eggs are dominant, so all the eggs should receive at least one copy of O. I'd expect many pale green eggs, maybe some muddy olive. Possible blue, but the Isbar would have to be homozygous for Pr, Prpr.

That's all I can tell you
 
Thank you sjango! That is really informative and helpful. So if I'm understanding this correctly, the reason some Isbar throw brown egg layers is because a parent is Oo instead of the more correct OO - do I have that right?
 
Thank you sjango! That is really informative and helpful. So if I'm understanding this correctly, the reason some Isbar throw brown egg layers is because a parent is Oo instead of the more correct OO - do I have that right?
You are absolutely correct. If both parents are Oo, then 25% of the offspring will lay brown instead of green!

A well maintained line of Isbars should not have any offspring that lay brown
eggs.
 

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