White Inhibitor Speculation: Color-Headed Dogs
October 9th, 2020 1:45 AM
This involves the Color-Headed White pattern I've noticed in Dalmatians.
Relevant Image, denoting four litters I've bred in the last six hours:
Green text (M): Male
Pink text (F): Female
The first two (top left, middle) share the same father, but otherwise there are no repeated dogs.
CWH: Color-Headed White (CHW is used below.)
N: Non-Color-headed dog
p, ep: Piebald, Extreme Piebald (all dogs have the same piebald gene combo)
?: dogs with Colorhead marking do not specify piebaldism type.
The orange male (top right) has an ID in the 200ks, which possibly predates the addition of this, but an older custom (here) has shown this unlikely to be completely true, and implies that the White Inhibitor might actually have existed in game for a long time prior to it being visible to us. Because of this dog, I've developed the following theory.
Note that the top left and middle pairs confirm the following:
-CHW is not a true recessive, as two CHW dogs have produced normals.
Note that bottom left confirms the following:
-CHW is not dominant, as two Normal dogs produced all color-headed pups.
-CHW is not heterozygous, as two Normals could only produce homozygous pups of the same type if this were true.
Now, going back to this dog:
Look at their color.
aw/at B/bS KB/ky D+/D+ Eg/e C/C x/x g/g m/m h/h sp+/si- T/T At/As v/v +/+ N/N N/N N/N N/w- chch/chch Intint/Intint
(Let's make this easier to read!)
aw/at .. B/bS .. KB/ky .. D+/D+
Eg/e .. C/C .. x/x .. g/g
m/m .. h/h .. sp+/si- .. T/T
At/As .. v/v .. +/+
N/N .. N/N .. N/N .. N/w-
chch/chch .. Intint/Intint
A quick glance at the Colour screen when creating a new breed shows this:
In the custom color shown above, we had 21 genes. We've got 19 options here. This leaves us with two unaccounted for.
Now, KIT can also be N/N, so let's assume the other three N/N genes are White Inhibitor.
Finally, my theory:
We have three pairs (N/N, N/N, N/w-).
When you really look closely, and throw in Polygenetics, and assume that N stands for Normal in the genotype as it does in the health genes, we can assume that (w-/w-) would make a difference.
The White Inhibitor gene has three pairs, and any given one being (w-/w-) would result in a color-headed white dog. All three pairs containing (N/+) would be a non-color-headed dog.
This means that the normal parents likely looked something like this:
N/w- N/w- N/w-
N/w- N/w- N/w-
Meaning that they had a high chance to throw color-headed dogs.
HOWEVER--I would like to inspect other lineages involving color-headed dogs to see if I could prove this. If anyone has old customs that show (w-/w-), we might be able to prove this rather easily by breeding to known carriers. Or, by tracing pup lineages and getting a rough percentage of color-heads from Normal lines, and normals from Color-heads, we'd be able to roughly figure it out.
If anyone has a proposed theory that's unrelated to the above, I'd love to hear it! Feel free to post below or ping me on Discord (I am in the official channel.).
I will update this post with further data if I find it!