I will explain the genetics just to make the whole thing a bit clearer
We'll call the allele for wild "W" and the allele for silver "w". This is kind of a convention in genetics that when one gene is the dominant gene you do it in caps and the recessive in lowercase. The gene will have an official name somewhere. You also sometimes see the version of a gene that causes an effect shown with a + and the version that does not cause the effect -
We'll stick with W and w
In the case of this pair of alleles, if a bird has just one copy of the dominant allele W it is going to come out looking like a wild type regardless of whether the other allele is W or w. So the genetic makeup of a bird that appears wild, could be WW or Ww. When a bird has only w alleles ie is ww, that is when it is a silver. A silver can only be ww, which means it only can pass w allele on to its offspring which means if you breed a ww (silver) to a ww(silver), there is no possible way it can produce wild coloured offspring.
If a bird is heterozygous (aka "split") meaning it has one wild W allele and one silver w allele, it will look wild but can have silver offspring if it is bred to another Ww or to a silver (ww). Geneticists use what are called punnet squares to predict outcomes, I will *try* to make something that looks like it on here
x | W | w
___________________
| |
W | WW | Ww
| |
____________________
| |
w | Ww | Ww
| |
What that really yucky punnet square represents is that each parent passes on one allele to its offspring. So in the case of the Ww parent, each offspring gets either a W or a w allele. When both parents are Ww as in the punnet square, the offspring get either a W or a w from mum, and either a W or a w from dad. Meaning there are four possible combinations of alleles any offspring could receive although in this case two of them are going to work out the same. The punnet square shows that crossing two Ww produces 25% ww (silver) 50% Ww (wild carrying silver) 25% WW (wild not carrying silver). Note that the punnet square only represents the statistically expected outcome, not the exact number of offspring you get. Like how if you flip a coin the odds are 50% either way and yet if you flipped a coin 100 times, most of the time you wouldn't get 50 tails 50 heads.
If a Ww (wild carrying silver) bird is crossed with a ww (silver) bird, you will get 50% Ww (wild carrying silver) 50% ww (silver)
If a WW (wild not carrying silver) bird is crossed with a ww (silver) bird you get all Ww. So all the birds are wild in appearance but carriers of silver
If a WW (wild not carrying silver) bird is crossed with a Ww (wild carrying silver) bird you will get 50% WW (wild not carrying silver) 50%Ww (wild carrying silver)
The terms recessive and dominant are much abused. By people on this forum even. The W allele we have discussed is dominant over the w alllele. This means any bird that has the W allele will appear wild even if it has the w allele (is a Ww). The w allele is recessive. Recessive alleles show up in the absence of dominant alleles. In this case, in a ww bird. The important thing to take from this is, a bird showing a recessive trait cannot possibly even if it really wants to carry a dominant allele for that trait. So if you breed two silvers together you can only get silvers, try as you might. Go right ahead and try if you don't believe me.
I hope this satisfies your curiosity and proves my credentials as a genetics graduate (although your kids will be learning this level of stuff at highschool)
