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Genetics of egg color

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Lindsay Helton:
Can someone explain the genetics behind egg color to me? I have been focusing on type the last three seasons, while of course only setting blue eggs, but this year I would like to focus in on egg color more closely. I have marked the eggs that are the deepest shade of blue, and plan to mark those chicks for identification later on.

Is egg color influenced by the cock, hen, or both? I read somewhere online that it is influenced by around 13 genes...I don't know if that is true or not. If anyone has any reading material that they can recommend, I would be appreciative.

Each year I hatch and keep several hundred chicks. Unfortunately, this season a wheaten pullet that hatched from a blue egg grew up to lay a pink egg. My bloodline originated from one of the directors, and they are definitely true Ameraucanas. The other pullets that I kept from that pen lay blue eggs. Do I need to consider culling the cock from that pen?  I raise for show and he has great type, so I would prefer not to. However, I do want to be sure that I keep egg color in mind. It is definitely a balancing act. Most of my pens are set up with one cock over five hens, so I can't say for certain what hen she came from. I would like to get my pen sizes smaller, say one cock to three hens, but that will involve building more pens, and I am trying to give my husband a little break from coop and pen building. LOL!

Susan Mouw:
I posted a link to an article about this some time ago.  I'll see if I can find it and repost it.

Susan Mouw:
I found it. :)  See if this answers your questions...

http://ameraucanabreedersclub.org/forum/index.php/topic,2636.msg18898.html#msg18898

Lindsay Helton:
Thank you Susan!!!

I am trying to be sure I understand completely. I used B to denote egg color.

I gathered from the article that egg color is simple dominant.

Since one of the pullets grew up to lay pink eggs, the cock would have to be carrying a recessive allele for non blue eggs (I'll name him Bb), as well as one of the hens in that pen (I'll name her Bb as well) thus creating the pink egg layer, right? I do not know definitively regarding what color egg the cock was hatched from, since he wasn't hatched here, although I'm sure it was from a blue egg because I know the breeder well.

The hens that were in that particular pen have been culled (due to age). But regardless, that would still mean that the cock is not completely dominant for blue eggs right? So he would be Bb instead of BB?

So how does an off colored egg layer happen from a pullet that hatched from a blue egg?

Is it because the offspring only receive one allele from each parent? So in the case of a Bb cock mating with a Bb hen (a hen that lays blue eggs but carries the recessive allele), there would be a 25% chance that the chicks inherit the recessive trait for non blue eggs (bb)?

Sorry if I am making this more difficult than it is. :) I am not well versed in genetics. Lol

Susan Mouw:
You have it exactly right.  If this is a single gene recessive trait, as put forth by Punnett, then both the hen and the cock are carrying at least one copy of that recessive, in order for any chicks to have both copies and show the recessive trait.

So, yes..the cock was Bb and the hen was Bb.  So you have a 25% chance of BB (pure for blue eggs), 50% chance of Bb (mixed for blue eggs. Eggs will all show blue, but can pass on the trait for non-blue to offspring), and 25% chance of bb (pure for non-blue) in the chicks.

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