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genetic resources for (budgerigar) breeders
So my questions is, why is the dominant pied called dominant? How can it be considered dominant if there are a certain percentage of normal chicks produced? I would have thought dominant pied meant that it was dominant over any other colour? Or does it merely mean it is a dominant version of the the pied gene, as apposed to the recessive pied gene? I am confused?
First dominant pied and recessive pied are completely different mutations and are genetically not related. That's the first element causing confusion.
Dominant indeed is on the gene level. Birds have (almost) all genes in pairs. Let's call the dominant pied gene P. The normal version of this gene (i.e. not pied) is P+. If a bird has both type of this gene: so one normal (P+) and one pied (P): P+/P, the definition of dominant is that you will see that colour in the bird. In this case dominant pied.
For a recessive mutation like blue (bl) it's the other way round. A bird that is normal and blue: bl+/bl will be normal as the blue is recessive.
Now why does a dominant pied when paired to a normal produce both normals and pieds? Well, the pied has the genes P+/P and the normal has the genes P+/P+ (both normal, otherwise it would be a pied). Now the offspring will be a combination of both parents, so you need to combine the genes of the father with a gene of the mother. In this example there are two possible combianations: P+/P+ and P/P+, or normal and pied.
Now birds with two dominant pied genes exists: P/P. These are pied birds (with bigger pied pathes). And these will produce 100% pieds when paired to a normal.
Hope this helped,
(C) Bert Raeymaekers