#epistatic white

[warriorsochelp]

Which type of white is linked to deafness, do you know? I know that sufficiently high-grade white spotting can "cover" a cat's genetic color, and that there's another type of "dominant" white, but I wasn't sure which is linked to deafness.

I’m going to go into a little more detail below, but tl;dr it’s dominant white and only for those with blue eyes

Okay, so there are actually three different ways you can end up with a solid white cat: high-grade white spotting, albinism, and dominant/epistatic white.

High-grade white spotting is not associated with deafness. Cats with high-grade white spotting are very likely to have blue eyes or heterochromatic eyes (with one eye being blue and the other something else), but they can have any eye color that’s possible for a cat. White spotting is an incomplete dominance situation, so to be solid white from high-grade white spotting a cat has to have two copies of the white spotting allele (so both parents have to have some white), and additionally the random chance or other polygenetic factors while the cat is in the womb have to go just right.

Albinism is not associated with deafness, although albinistic cats do have other problems (particularly light sensitivity because of their inability to produce melanin). Cats with albinism can have either blue or red eyes, depending on which albinism alleles they inherited, but even blue-eyed albinos can be distinguished from other blue-eyed white cats. For one, the shade of blue is very pale compared to other blue-eyed cats, but also, if you watch light reflect off an albino (or colorpoint, fwiw) cat’s eyes, it’ll reflect off red instead of the typical greenish hue. Albinism is pretty rare because both albino alleless are recessive not only to the ‘normal coloration’ alleles, but also to colorpoint alleles (which are on the same gene). So both of an albino cats’ parents have to at least carry the albinism gene.

Dominant/epistatic white is the one that’s associated with deafness. However, it’s only associated with deafness among cats with blue eyes. Cats that are dominant/epistatic white can have either blue eyes, orange eyes, or one blue eye and one orange eye. Dominant/epistatic white cats with blue eyes have a much increased risk of deafness, and heterochromatic dominant/epistatic white cats will often be deaf in one ear on the side with the blue eye. Dominant/epistatic white is, as you might guess from the name, dominant, so a cat that’s dominant/epistatic white must have one dominant/epistatic white parent. 

~E

[sparrowminder]

Someone (Annmy on deviantART) said that all the white genes in a cat, including the white spotting one can interfere with a cat’s ability to hear more than at the normal rate, but isn’t it only the epistatic white gene with blue eyes caused by said gene has a slightly higher than normal risk of impaired hearing or deafness and that the white spotting 100% white cat with blue eyes has a normal risk of hearing loss or impairment just like any not all-white cat?

Nope, it’s only epistatic white. The reason for this is that the two genes use different mechanisms to restrict pigment. Epistatic white interferes with melanoblast (color cell) formation and migration, and can also affect closely related cells in the eyes and ears. If it affects the eyes, it causes the eyes to be blue, and if it affects the ears, it causes deafness. If a dominant white cat has blue eyes, it is more likely that the ears are also affected. In addition, if they have only one blue eye, it is more likely that they will be deaf in the ear on that side.

With white spotting, melanoblasts form and migrate evenly, but as the embryo grows the layer “cracks apart”, giving us the distinctive pattern of white spotting. This can affect the eyes, especially if the white reaches around the eyes, but it does not cause any notable increase in the rate of deafness.

For more information and statistics about epistatic white, blue eyes, and deafness, Messybeast has a page that explains it quite well. The rate is much higher than I thought - about 60-80% of white cats are deaf!

[warriorsochelp]

i have a pure white blue-eyes tom, who's deaf in one ear, and a pretty silver molly with chinchilla fur that makes her fur sparkle. Can the two have white kits? or are they going to be silver, like the molly? Thanks in advance!

Tl;dr: both!

The kind of whiteness your tom has, epistatic white, and can be passed on to kits easily--you actually have to have at least one epistatic white parent to have an epistatic white kit. If he has one epistatic white gene, each kit has a 50/50 chance of being epistatic white themselves. If he has two epistatic white genes, every kit will be epistatic white. Whether he has one or two is up to you unless you already have this tom’s parents picked out--if he has one epistatic white parent, he’ll have one gene. If both his parents are epistatic white, he’ll have two!

With a chinchilla mother, the non-white kits (if any) have some interesting options, but in order to say anything about the possibilities there, I need to know what the white tom’s color would be if he didn’t have the epistatic white gene--that gene masks the cat’s real color and pattern with white, but he’d still pass one genes from the covered-up color and pattern. If you want to know the non-white kit possibilities, feel free to send another ask!

~ E

[warriorsochelp]

One of my oc's is an epistatic white with a black molly carrying dilute as a mother and an epistatic white as a father who is cream and 50% white genetically. Is it right to say she could genetically be a dilute calico? Also what portion of her kits would be epistatic white if she mated with a non epistatic white cat? She also has 3 siblings that are all the same colour as her, but are grey and white and dilute torties underneath. Is this right?

This is totally do-able, as long as the grey-and-white siblings are toms.

Since your OC has only one epistatic white parent, she definitely carries the non-epistatic white gene, so each of her kits has a 50% chance of being epistatic white themselves, provided their father isn’t epistatic white.

So yeah, seem right! Good job!

~ E

[warriorsochelp]

Does orange mask epistatic white? Or is it the other way around?

Epistatic white masks everything else.

~ E

[warriorsochelp]

Hi! So I saw that post titled family conundrum and I was a little confused because you mentioned that epistatic white cats can only have blue and/or orange eyes? I was wondering if you had a source for that because I know on the messybeast section for white cats they have an image of an epistatic white with green eyes so I just wanted to double check. Thank you!

My source for that has been Joumana Medlej’s guide to cat colors, the infographic we often post here. Under epistatic white and eye color, it states that for epistatic white, the eye colors “are inevitably” blue and/or orange, but that a solid white cat can have any eye color if it’s genetically 100% white spotting instead of epistatic white.

That picture in the messybeast guide does confuse me, since in the paragraph above those pictures it even says “Dominant white masks all other colours and cats may have blue, orange or odd eyes”. My instinct is that labelling the solid white cat with green eyes as dominant white was an error, and that Mikey does not actually have the dominant white gene but is actually 100% white-spotted.

That said, if anyone has any good sources that say otherwise, send them my way and I’ll edit these posts to reflect that.

~ E