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Aaaa!Yes.
Yes.
Yes
Um, sort of.
The dominant allele gets a capital letter, and the recessive one gets a lowercase letter.
So you just list whichever is present, the dominant or the recessive trait.
Example with blue:
Bl/Bl is splash (two copies of the blue gene, which is dominant.)
bl/bl is black (two copies of the not-blue gene, which is recessive.)
Bl/bl is blue (one copy of the blue gene, and one copy of the not-blue gene.)
Example with Dominant White:
I/I is pure for Dominant White.
I/i has one copy of the Dominant White gene, and one copy of not-Dominant-White
i/i is pure for not-Dominant-White
With many of the genes, we have a name for the mutation (blue, Dominat White, recessive white, etc.) But we don't have a good name for the other form of the gene, the original wild-type form.
I've settled for calling them not-blue, or not-Dominant-White, or not-recessive-white, just to point out that they are a gene at that place, but it's the gene for not having that trait. (I don't know of anyone else who habitually refers to them that way, but people seem to understand well enough what I mean, so I've kept doing it.)
Sometimes the mutation is dominant (Dominant White, Blue) and sometimes it's recessive (recessive white, mottling, lavender.)
I had a few Yokohamas at one point, too. Mine were all females. I liked them quite well, except that they made a LOT of noise (egg song too many times a day). I gave them to some friends, where they flew out of their pens and got killed by various predators (many other breeds of chickens were staying safely IN the same pens.)
So the Yokohamas I had didn't rate too high on survivability!
Incomplete dominance means that one copy of the blue gene has an effect (turns black to blue) but two copies of the blue gene have a stronger effect (turns black to splash.)
Complete dominance is when one copy of a gene (not-recessive-white) has the very same effect as two copies of that gene. You cannot tell by looking at the chicken whether it carries one copy of the recessive white gene or whether it is pure for not-recessive-white.
I think they had splash birds, and mistakenly thought they had white birds. (So they crossed a splash with a black and got blue-- no surprise there!) That is the simplest explanation that covers the "facts" in the story.
Or they had a bird that was splash, but looked white because it also had one copy of the Dominant White gene. So when they crossed it with a black bird, they got some white chicks (Dominant White, also genetically blue but you can' t see the blue) and some blue chicks (no Dominant White, so you are able to see the blue.)
Or they could possibly have had birds that were white from recessive white, but also splash. Crossing those to a black bird would have given blue chickens (black x splash = blue, and recessive white x not-recessive white gives birds that are not white.) Or to use symbols, the chicks from such a cross would be Bl/bl C/c.
But I think they most likely had splash birds and were CALLING them "white."
Yes, a "white" bird created with Dominant White is genetically an all-black bird (so no red can show), and then the black is turned to white by Dominant White.
You seem to be grasping a lot of this very quickly, so your brain probably is working very hard!
Yes, black can be complicated!
Blue is the name for an actual allele. It just happens to be incompletely dominant, so only one copy of the blue allele is needed to make a chicken look "blue."
Dominant White is a separate gene, at a different locus.
Blue is much easier if you leave Dominant White out of the picture.
Dominant genes get capital letters, whether they are completely dominant or incompletely dominant. Recessive genes get lowercase letters.
The e-locus is definitely interesting, but also complicated!
It affects the adult color of the chicken, but also the color of the down when the chicks hatch. And with at least 5 alleles, and many ways to combine them, and many other changes caused by other genes-- it can be very hard to figure out!
I've learned a lot from it too!
From what you have described of your birds, you probably do not have Extended Black in your flock.
--Extended Black chicks are often colored like little penguins, in black and yellow.
If you want to look up pictures, here are examples of some chickens that have Extended Black:
Barred Rock and Cuckoo Marans (white barring on the black)
Blue Cuckoo Marans (blue gene dilutes the black, and white barring on that.)
Mottled Ancona (mottled gene on the black)
Lavender Orpingon (lavender gene dilutes the black)
Chocolate Orpington (chocolate gene dilutes the black)
Pearl Old English Game Bantam (lavender gene dilutes the black, AND mottled gene makes white dots.)
White Leghorns (Dominant White changes the black to white. But they often have blue, barring, and various other genes too-- it's like someone stacked up every possible gene that could make black lighter or remove it in places, and put them all in the same chickens to make them REALLY white!)
Extended Black written as E means it is dominant over the other alleles at the e-locus.
Dominant White written as I means it is dominant over other alleles at the i-locus.
Recessive white written as c means it is recessive to other alleles at the c-locus.
Whether a gene is dominant or recessive at its own locus does not tell you how it interacts with genes at a different locus.
I think you are likely to be right about them being e+ or eb at the e-locus, but I'm not positive either.
I've had times when I really wanted to know what genes something had, so I certainly understand that!
I did say my brains fried right?

I completely forgot that dominant white masks black, not leaks color! I do actually remember that...most of the time. Eventually I'll remember it all of the time!
Your explaination of blue makes sense now and I agree...those original white birds must have carried splash. So it is a gene and not an interaction. Very nice explaination!
I kept hanging up on the "expressed in a reduced ratio" and thinking that must mean it's not a gene but an interaction between genes. I thought reading Mendel's theory might help me understand the interactions between genes but but...sigh. I do like your explaination of incomplete/complete dominance. That made sense.
Ok. Let's try again

So....all the letters we use to describe phenotypes are genes and the interactions between them that effect phenotypes are understood from reading the gene combinations once you know enough about how the individual genes work.
Each locus requires 2 alleles...wait...or 5...ouch...
Hmm. Ok. So maybe better to say that each parent gives 1 allele so each locus recieves 2 alleles for each spot that requires an allele? So we state the visible allele and know that there is a paired allele there that may be visible as in cc. Or it might be invisible and only show through future breedings as in Cc. And C is not the absence of an allele there but the wild type which may or may not have a visible effect but isn't significant enough to be named or is unknown.
Whew...did I get it right?
I think I'll start on that kippenjungle site tonight. It'll make nice bedtime reading. I started to read it the other night and got sidetracked. Did you know that kippenjungle site has calculators for finches, squirrels and all kinds of things? It's amazing! Anyways, genetics may take a bit to understand but it's fascinating.
I loved seeing how the chicks are effected by the genes, and the pearl old English are absolutely gorgeous! I read somewhere that the lavender fades out if bred lav to lav too much and needs an occasional dose of black added back in? I have my hands full on chickens right now...but someday I might have to get some of those if I can find them.
Your poor Yoko's! Mine are pretty quiet...well, maybe it seems that way because their nests are further from the house then my little chickens. They get more freedom then the little guys so they often end up in my garden...but their house is about half an acre from it. My roosters crow so rarely that it sometimes startles me...their voice is so much deeper then my other birds!
Well...at least they made some predators happy
