Quote:
What are generally termed "dark factors" in other birds are typically incomplete-dominants. Having one gene gives one dose of "dark" and having two genes gives a double dose of "dark." Birds with one dark factor are not as dark in appearance as birds with two dark factors. Other "factors" are also incomplete-dominants. An example is Andalusian blue in chickens. Those with one gene are "blue" and those with two are "splash." Midnight is a color caused by a recessive mutation, and is visual only when there are two Midnight genes present, thus it is not a "factor."
Peafowl have only one family of pigment -- melanin. Color in them is caused by a combination of pigment and feather structure. Alter either (or both) and the "color" presented will be different. If one "color" is caused by an alteration in the feather structure (causing the light to be refracted differently, and thus we perceive a different "color"), and another "color" is caused by a change (increase or decrease) in the amount of pigment, then they most certainly can be combined, as the genes are doing two different things (one might increase the amount of pigment, and another alters feather structure to change light refraction). I don't understand how, despite this, people here are claiming that it's impossible for peafowl to be homozygous for two different color mutations at the same time, and thus look different than either color independently and different from regular IB. I can understand someone saying he hasn't seen it, but to just say "impossible" is not logical.
People here seem to be hung up on the term "color" and I think it is believed that somehow the Purple gene causes a purple pigment, as opposed to a blue pigment. This is completely incorrect. Purple affects the amount of pigment and/or alters the feather structure. There is no blue or purple or green or cameo or peach or opal or charcoal "pigment" in peafowl. Melanin is the pigment in ALL. All color in peafowl is the result of an interaction between amount and distribution of melanin and feather structure. Mutations affect this interaction simply by altering pigment distribution and/or feather structure. I'm in my fourth college course of genetics (crop genetics and livestock breeding at Cornell, and behavior genetics and human genetics at University at Buffalo), so I'm rather well-versed in understanding how genes interact.
I do hope I have something in my email box tomorrow that can put an end to this.
:-/