Silkie Genetics

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Silkie Genetics

Dr. W.F. Hollander
Ames, IA

Does a Silkie have genes? Of coarse! How many? Hmmm – just as many as other chickens – Thousands. Oh…But I meant SPECIAL genes!

Special? How special? Absolutely unique? what’s the reference? Well, let’s first consider the plumage structure. Even a blind person can recognize silkieness – it is unique. The reference? Normal of coarse. Not frizzle or some other condition. Normal plumage is necessary for a chicken to survive without human care.

Early Mendelian investigators suspected that a special gene is responsible for silkiness, and breeding tests supported the idea.

The method is simple – cross with normal and see what results, then get a second generation and count the individuals according to type. A simple ratio (such as 3:1) is evidence for single gene difference. In 1921 Sara V.H. Jones reported her test results and reviewed previous studies. They all agreed that a single gene, recessive to normal is the culprit.

Ordinarily when such a conclusion has been reached the researchers give the special gene a reminiscent letter symbol, lower case for recessive, capitol for dominant (example B for barred). But Ms. Jones neglected to do it. A few years later (1927) in a more extensive report, L.C. dunn and M.A. Jull assigned the Silkie gene the letter h.

OK small letter for recessive, but why that letter? Not as strange as you’d think – under a microscope silkie feathers had been shown to lack the tiny hooks that hold the barbules together in normal feathers. Hookless!

What about other special charactoristics in our breed? Here’s a list of those with gene symbols as far as assigned:

Silkie feather: h (hookless)
Rose comb: R
White plumage colour: c (colourless)
Crest: cr (double letter because the above had taken the single letter)
Muff-beard: Mb
Polydactyly (five toes): Po
Black skin: Fm (Firbromelanosis)
Booted: F
Short flight feathers and tail feather

That’s at least nine special genes, the most for any chicken breed! Just happenstance? No! Somebody put them together centuries ago. A dificult project, requiring many years, and not one for poor people. My guess is that a Chinese Emporer, probably the Han Dynasty, had a core white silkie stock and gradually added the other (dominant) genes. And this is centuries before Mendelism! I’ll bet the royal kitchen got thousands of cull birds!


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