ameraucana genetics question

[Chris383]

Let me start off by saying I understand amerucanas and ee era aren't genetically pure to begin with. ... But my question is about the genetics of the coloured eggs. Specifically if an amerucana or ee rooster bred with a chicken that produces Brown or white eggs, what colour eggs would those offspring lay? Random chance or does egg colour genes come from one parent

 

[Ridgerunner]

Good question. Each parent will contribute genetics. There are two parts to this answer.

An egg’s base color is either blue or white. Green or brown is just brown laid on top of the base color. You might think of it this way.

Base blue + no brown = blue
Base blue + brown = green
Base white + no brown = white
Base white + brown = brown.

There are a whole lot of different genes that contribute to brown. The actual shade of brown or green will depend on which, if any, of those “brown” genes get passed down. Some are dominant, some recessive, some partially dominant, some only act if another specific gene is present. That’s why you can get so many different shades of brown or green. If you know the shade of brown or green of the parents you can make an educated guess as to what shade you might get but you can also get some pretty good surprises. That’s the first part.

Each parent contributes one gene to the gene pair that determines base color. Blue is dominant. That means if just one of the genes at that gene pair is blue, the base color will be blue. The genetic symbol used for the blue gene is a capital “O” since it’s dominant. A small “o” represents the recessive white gene. So:

• OO gives a base blue egg
• Oo gives a base blue egg
• oo gives a base white egg.

When a chicken gives a future offspring a gene from this gene pair, it’s random which gene, left or right, gets copied. If it is OO the offspring will get an O; oo an o; but Oo it could be either.

An Ameraucana by definition is pure for the blue gene. That means it is OO and the offspring will get a blue gene. All pullets from an Ameraucana rooster will lay a base blue egg. That parts easy.

The problem with an EE rooster is that you don’t know if he is OO, Oo, or oo. Roosters don’t lay eggs so you can’t look at the egg color to determine anything. You don’t know what genetics he has. If he is split (Oo) he could pass down either. There is no set answer for an EE. It could be anything unless you know a lot about the genetics of both of his parents. At least with a hen you know she is OO or Oo if she lays a base blue egg.

 

[dheltzel]

Perfect explanation of the blue egg gene by @Ridgerunner . I would add that in my experience "O" is only partially dominant, and that variations in the depth of the blue color can be (at least partially) explained by some hens being Oo and some OO. The OO hens will lay a deeper blue colored egg. The blue also tends to get lighter as the laying cycle goes one, so the first eggs laid by a pullet or the first after a molt, may be a little darker blue. That seems to be a very subtle effect, or maybe I just don't pay that much attention to where in the cycle they are.

I use a Black (purebred) Ameraucana roo over a barred white egg laying hen (Barred Hollands or California Greys) to get a black sexlink that lays lots of light blue eggs. I highly recommend this cross, though the eggs are not as deep a blue as a pure Am or a Cream Legbar (both OO).

Pure Ameraucana roos are not that uncommon, if you watch the local ads you might be able to buy one for cheap, and he will be a much better sire for your future crop of blue and green egg layers. If you get a purebred Am, do not get a blue or splash one if you want to make black sexlinks, the blue chicks are very hard to sex. If you're not concerned with sex linkages, then blue or splash will make for some pretty chicks.

 

[Ridgerunner]

Dheltzel, perhaps you can help, I think so. I’m not quite sure what the difference is in “partially” dominant and “incomplete” dominance. I think “partially” is like the blue egg shell color you described (had not heard of that being partial before) or maybe the effect of two barred genes versus one giving you an overall lighter bird. I think “incomplete” is like the blue feather gene where with two copies you get Splash, one copy you get Blue, and no copies you get Black. I’ve been wrong before. Just ask my wife.

Chris, sorry for the hijack but I’m trying to grab a learning moment here.

 

[dheltzel]

Dheltzel, perhaps you can help, I think so. I’m not quite sure what the difference is in “partially” dominant and “incomplete” dominance. I think “partially” is like the blue egg shell color you described (had not heard of that being partial before) or maybe the effect of two barred genes versus one giving you an overall lighter bird. I think “incomplete” is like the blue feather gene where with two copies you get Splash, one copy you get Blue, and no copies you get Black. I’ve been wrong before. Just ask my wife.

Chris, sorry for the hijack but I’m trying to grab a learning moment here.

I think the 2 terms are used interchangably, I don't know of any particular distinction, and in my mind the 2 examples you gave are really the same at the level of figuring out the inhereritance. I think of barring as each "dose" make the bird whiter, that is sort of the same as BBS blues, where each dose dilutes the black, it's just suffuse, not distinct lines. "O" seems to add blue to the shell material, and 2 doses gets more of the blue "dye" in there. I wish someone would analyze the shells and see if the amount of the chemical responsible for the blue color was present in ratios that match the number of copies of the gene, but I doubt anyone with the knowledge and equipment cares enough to ask that.

The inheritance of brown egg color intrigues me, but again I don't have any way to get theories tested, so I just speculate.

 

[donrae]

I've also had good luck putting pure Ameraucana roosters over white egger hens. Lots of large, pale blue eggs