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So white is independent of color? So someone mentioned earlier in the thread, I think, that sometimes it does create unpredictable lighter variations (or that's how I interpreted what was said). Is there an unpredictable 'dimmer switch' action
No, white does NOT dilute. There are two different white genes. Recessive white is indeed an offswitch. Tim can explain it better, but at the cellular level it prevents the formation of all pigment. It can be leaky, allowing a bit in occasionally on a feather here or there, but overall is pretty non-leaky. Dominant white, on the other hand works differently, and is very leaky. It is more like a filter than an offswitch--it doesn't prevent pigment from forming, but it does prevent it from being placed in the feather (Tim, if I got any of this wrong, please correct me). One copy prevents black pigment from entering feathers; two copies also prevents red pigment. Exchequer leghorns are leaky dominant white. Red pyle is dominant white.
So white is independent of color? So someone mentioned earlier in the thread, I think, that sometimes it does create unpredictable lighter variations (or that's how I interpreted what was said). Is there an unpredictable 'dimmer switch' action

No, white does NOT dilute. There are two different white genes. Recessive white is indeed an offswitch. Tim can explain it better, but at the cellular level it prevents the formation of all pigment. It can be leaky, allowing a bit in occasionally on a feather here or there, but overall is pretty non-leaky. Dominant white, on the other hand works differently, and is very leaky. It is more like a filter than an offswitch--it doesn't prevent pigment from forming, but it does prevent it from being placed in the feather (Tim, if I got any of this wrong, please correct me). One copy prevents black pigment from entering feathers; two copies also prevents red pigment. Exchequer leghorns are leaky dominant white. Red pyle is dominant white.
My understanding is that black acts similarly in ducks, but that it's incompletely dominant letting some of the original color come through (but that's not what causes the partridge color right?). Does it allow for the lavender variations? OOOOhhhh my head always hurts when I try to go here.
I don;t know anything about duck genetics, so I cannot relate how chicken genes relate to duck genes--Henk does know both, so maybe he will chime in. Partridge is a hobby name that can mean a couple of different things. If you are talking about a penciled bird such as a partridge rock, wyandotte, cochin or silkie, it is the interaction of a specific
black allele, e^b (brown) combined with Pg (pattern gene). Lavender is caused by a double dose of lav (lavender).
Chicken plumage can contain only two pigments: black (eumelanin) and red/gold (pheomelanin). There is a basic pattern of which of these two colours appear where on the body of a male vs female. Various genes modify which colours go where (extending or restricting the colours to/from these areas), dilute or deepen pigment tint/shade (which may also alter the hue), or create patterns on individual feathers.

I don;t know anything about duck genetics, so I cannot relate how chicken genes relate to duck genes--Henk does know both, so maybe he will chime in. Partridge is a hobby name that can mean a couple of different things. If you are talking about a penciled bird such as a partridge rock, wyandotte, cochin or silkie, it is the interaction of a specific
black allele, e^b (brown) combined with Pg (pattern gene). Lavender is caused by a double dose of lav (lavender).
Chicken plumage can contain only two pigments: black (eumelanin) and red/gold (pheomelanin). There is a basic pattern of which of these two colours appear where on the body of a male vs female. Various genes modify which colours go where (extending or restricting the colours to/from these areas), dilute or deepen pigment tint/shade (which may also alter the hue), or create patterns on individual feathers.