Mottled Pekin Bantams have the same genetics(as far as phenotype goes) for the Mottled Pattern. That is recessive mottling on a self black background.
E/E(extended black) and recessive mottling(mo/mo) that is very simple
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Currently there are 4 known mutations on the mottling allele, possibly 5.
Mo+/Mo+ = All black, the dominant wildtype non mottling allele
mo/mo = The most known type of mottling found in European/American breeds, found in mottled houdan(genetically sequenced)
mo^J/mo^J = This is an allelic mutation of mottling found in Japanese breeds(have been genetically sequenced and found to be different)
mo^W/mo^W = This is an allelic mutation of mottling that makes the birds completely white, it was found on White Ohiki breed and it is currently known as Tyrosinase Independent Recessive White (mo^w)
mo^U/mo^U = Millie Fleur d^Uccle were also sequenced for the mottling allele and no mutation was found. It is postulated by the research that the mutation is just outside of the coding region of the mottling allele
I also believe that the White Crest in Polish could be an allelic mutation(either inside or outside of the coding region)
An example of the Japanese mottling allelic mutation(mo^J) is The Mottled Japanese Bantam. It's entirely white with a black Head Spot
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You can find more info about mottling and it's allelic mutations here on my thread
https://www.backyardchickens.com/th...tling-and-its-many-allelic-mutations.1331859/