NERD ALERT!!!
NERD ALERT!!!
I'm going to get TECHNICAL!!!
The genetics are fun. The blue egg gene is represented by the upper case O, while the not-blue (white) gene is lower case o. The blue gene is dominant, so if you have one copy, the eggs are blue based. Both the hen and the rooster contribute a gene. So in my examples below, the gene combinations could come from either parent.
So if you have a one parent that is pure for the blue egg gene, or is OO, all offspring will get a copy of the blue egg gene regardless of what the other parent contributes. If both parents are pure for the not-blue egg gene, the eggs will not be blue based. Remember, all eggs are either blue or white based. The brown or green comes from an over-coating of brown and that is controlled by totally different genes than the ones we are talking about. The fun comes in when neither parent is pure for the blue egg gene. These are just odds for individual chicks. You have to have a lot of chicks for these odds to mean much in what you actually see.
So if one parent is OO and one is oo, all offspring will be Oo. If one parent is OO and the other is Oo, half will be OO and half Oo but all will have the blue egg gene. You just don't know which ones are pure.
For example, if both parents are Oo, then 1/4 of the offspring will be pure OO for the blue egg gene and 1/2 will be split Oo. These will all lay blue eggs. Well, the hens will. The roosters won't but they'll have the genetics to pass on. 1/4 will be pure oo and will not lay blue based eggs.
I think what most of us see is where one parent, usually the hen, is Oo and the rooster is oo. Here, half the offspring will be Oo and lay blue or green eggs and half will be oo and lay brown or white eggs. So you cannot count on an EE rooster to have any blue egg genes for his offspring unless you know that at least one parent was pure for OO. And if you want blue or green eggs, you should only hatch blue or green eggs from your EE's if they are with a non-EE rooster. And even with an EE rooster you can be uncertain.
One of the genetics gurus on here explained that the pea comb gene and the blue egg gene are real close to each other on the chromosome strand. They are so close that 97% of the time, they stick together when transmitted to their offspring. So if you have chicks that are not pure for the blue egg gene or the pea comb, the odds are pretty good that the offspring with the pea comb gene will have the blue egg gene since the pea comb is dominant over the not-pea comb gene. But for chickens that are not pure for the blue egg gene and the pea gene, there is a 3% chance they will not be connected. Those are still pretty good odds.
Where this might get a bit confusing is that there are other genes that also contribute to the combs appearance, the main one being the Rose comb gene. If the Pea and Rose are both present, you generally get a walnut comb. Of Rose and Pea are both absent, you get a single comb. There are other possible results too but I get real confused with those. The Rose and Pea are the main ones for most of us.
ColdUpNorth, I agree with you. The genetics are interesting.
