CandoAviary wrote:If I understand correctly just because you breed a green backed bird with a blue backed bird doesn't always mean that all the chicks will be split to blue... some may not inherit the blue factor at all.
It doesn't work that way - unfortunately
I'll try to explain why without getting too complicated.
Blue is the result of a bird carrying two copies of a recessive mutation. Because it's the result of two recessive copies, outside of a genetic anomaly like nondisjunction (which is how children are born with Down's Syndrome), there is no way the parent
can't pass on the trait to its offspring.
Think of it this way:
When a cell replicates, what basically happens is the DNA replicates and then divides - so each sister cell is essentially a mirror replica of the original cell.
With Meiosis, which is how gametes (eggs and sperm) are formed, the cells split a second time - so that the eggs and sperm have half of the normal number of chromosomes (so when egg and sperm come back together, the total number found in that organism is then present).
So let's take an example.
Let's say you have a hen that is BH PB Blue, and a cock that is RH WB Normal.
Genetically, this means the birds look like this:
Hen:
Z^b Y PP bb (Z is the sex chromosome, it has a recessive black allele, Y is the alternate sex chromosome which makes her a hen, there are two purple alleles present for breast color, and the bird is homozygous recessive (DF) for blue)
So the potential gametes (eggs) she can produce [genetically] are as follows:
Z^b P b
Y P b
Cock:
Z^R Z^R ww (Z is the sex chromosome, both have Red alleles present, there are two white alleles present for breast color, and there are no copies of blue present)
So the potential sperms he can produce are as follows:
Z^R w
Z^R w
Now, you add those two gametic possibilities together in all possible combinations (egg + sperm):
Z^b P b [+] Z^R w
Y P b [+] Z^R w
=
Z^b Z^R Pw b = RH/BH, Purple/White, Normal/Blue Male
and
Z^R Y Pw b = RH, Purple/White, Normal/Blue Hen
CandoAviary wrote:I recently saw an add that stated that they would not sell or claim split unless the bird had been bred and it was proven to carry and pass that gene.
Yes - because if you pair two /Blues together, you can't guarantee the babies that are /Blue versus the ones that are just Normal without first test breeding them.
This is different from pairing a Blue to a Normal or a Blue to a /Blue where it is definitive that non-blue babies are /Blue.
CandoAviary wrote:I have also paired a yellow back with a green back and have gotten regular GB besides the dilutes. I am wondering if these green backs will carry any gene as split/yellow????
Yellow is never carried "silently" since it is not recessive, but co-dominant. It will always display itself on the bird - Both by virtue of affecting the black, or visually appearing dilute or yellow, it will manifest itself on every bird that inherits it, so no bird can really be "split" for yellow without you knowing it.
What likely happened is the yellow male you paired wasn't DF Yellow, but SF. It happens a lot.
Either that, or I'm not sure if you colony breed, but it can be virtually impossible to determine the genetic background of a bird bred in a colony setting because the hens will often not be monogamous and other hens will also invade and lay eggs in other birds nests.
I have never known individuals colony breeding Goulds to not have these problems.
One step at a time, right?!