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Discussion in 'General breed discussions & FAQ' started by alohachickens, Mar 2, 2012.
For anyone interested in the "nitty gritty" on Smokey here's a link to the full PDF which includes color pictures:
and here's the Abstract:
The Dominant white, Dun and Smoky Color Variants in Chicken Are Associated With Insertion/Deletion Polymorphisms in the PMEL17 Gene
Abstract: Dominant white, Dun, and Smoky are alleles at the Dominant white locus, which is one of the major loci affecting plumage color in the domestic chicken. Both Dominant white and Dun inhibit the expression of black eumelanin. Smoky arose in a White Leghorn homozygous for Dominant white and partially restores pigmentation. PMEL17 encodes a melanocyte-specific protein and was identified as a positional candidate gene due to its role in the development of eumelanosomes. Linkage analysis of PMEL17 and Dominant white using a red jungle fowl/White Leghorn intercross revealed no recombination between these loci. Sequence analysis showed that the Dominant white allele was exclusively associated with a 9-bp insertion in exon 10, leading to an insertion of three amino acids in the PMEL17 transmembrane region. Similarly, a deletion of five amino acids in the transmembrane region occurs in the protein encoded by Dun. The Smoky allele shared the 9-bp insertion in exon 10 with Dominant white, as expected from its origin, but also had a deletion of 12 nucleotides in exon 6, eliminating four amino acids from the mature protein. These mutations are, together with the recessive silver mutation in the mouse, the only PMEL17 mutations with phenotypic effects that have been described so far in any species.
I love nitty gritty. If I had an hour and a chalk board ( old school) I could explain all the nitty gritty,
I was looking here: http://kippenjungle.nl/Overzicht.htm#kippengenen
So are you saying it operates more like dun and blue?
Oh no! Not the scratchy squeaky chalk! I'm getting goosebumps just thinking about it.
I am good with power point and all the techy stuff.
PMEL17 is gene that causes the same effect across different species of animals:dogs, horses, mice etc.
All of the alleles at the dominant white locus have a packaging problem. Recessive white just does not make the pigment- the c locus is responsible for making tyrosinase. Tyrosinase is an enzyme needed to make the melanin pigments.
With dominant white, the cells do not recognize the packages that hold black pigments so they destroy the packages and the pigments. It sounds strange but that is how it works.
The other stuff is difficult to explain. You would have to understand DNA structure, transciption and protein structure etc.
It says two doses needed to express in adult plumage so I can see how some would look at that and call it a recessive allele. Does anyone have any pictures of this color? The only one I've seen so far was in the journal article itself. In any event I'm assuming it's unlikely to have shown up in MadelineHere's cochin, but she says she only gets blue birds, no blacks.