Showing posts with label White. Show all posts
Showing posts with label White. Show all posts

Monday 31 May 2021

Sectoral heterochromia in an all-white cat

This is called sectoral heterochromia. It is rare and beautiful. No health issues. You do see it in domestic cats. The cat is all-white. It is the dominant white gene which affects eye pigmentation creation in the embryonic stage. It causes the removal of melanin pigment across a part of the iris. The blue color is caused by light refraction only (not blue pigment). The yellow by pigment (eumelanin). All-white cats have no pigment in the hair strands. This is why they can get sunburnt ears - no pigment to block sun and in any case the hairs are thin there.

The normal, most common, sort of heterochromia in cats is when they have odd-eyes. One eye is blue and the other is yellow normally. But there are various types of heterochromia and the one we see on this page is called sectoral heterochromia because each eye is divided up into two colours i.e. there are two sections to the eyes. Turkish Angoras sometimes have odd-eyes and they are favoured. They are often all-white cats too. The classic real Turkish Angora is all-white with odd-eye colour.

The cat below looks a bit like an Angora but is not to the best of my knowledge.

Sectoral heterochromia in an all-white cat
Sectoral heterochromia in an all-white cat. Photo:

Saturday 6 August 2011

White Bengal Cat

There is no such domestic cat as a white Bengal cat but there are snow and silver Bengal cats.

If you would like to read a bit about snow and silver Bengal cats please click on this link. Thanks.

A visitor writes about Banjo My Male Snow Bengal Cat.

Saturday 23 February 2008

Cat Coats White

Cat coats white is the last in a series on the cat coats. See all the articles by clicking on this link. In previous articles I have mentioned the Piebald gene (White Spotting gene). The gene usually (denoted by the letter "S") produces coats with white "spots" although "spots" is a misleading term. It produces areas of white leaving other areas in a wide range of colors and patterns such as Tuxedo, Tabby, solid colors and others (it is perhaps best to see all the posting to get the complete picture). 

All-white Maine Coon
All-white Maine Coon

 As can be expected if the white spotting works to maximum effect, then the whole of the cat will be white instead of areas of white, either small or large. Accordingly, one of the three genes that produces all white cats is the white spotting gene. Its actions are wide ranging as can be seen. That's why it is said to have "variable expression". It is called "recessive white" sometimes and I suppose because of its variable actions, it is "semi-dominant". 

 The genes that produce white fur cover up the other colors. Note: Albino cats are due to a different effect, the lack of production of color (see below). 

The other gene that produces cat coats that are white is the dominant white gene ("W"). This gene masks all other colors. 

As a result, it is impossible by looking at the cat to see what other genes are present. To use technical language, the gene W is "epistatic" meaning it masks all other color genes. There may be an exception in relation to eye color. The dominant white gene is a simple non sex related dominant gene. The white cat is not due to the presence of a number of piebald (white spotting) genes. 

Russian-bred all-white British SH
Russian-bred all-white British Shorthair kitten. Photo: Альбина Шконда питомник британских кошек Golden Leris nursery Golden Leris. WCF.

The W gene is at a different position on the chromosome to the white spotting gene and is therefore independent of the white spotting gene. Epistatic crudely means that where there is a competition between genes as to what color or type of coat will be seen (for genes involved with coat color), the gene whose phenotype (the appearance) is expressed (the appearance seen) is said to be epistatic. 

The W gene is also associated with deafness as it can affect the cochlea in the inner ear (the fluid filled chamber that converts sound waves to nerve transmissions to the brain). The gene produces blue, orange or odd eyes. If the cat has blue eyes there is a good chance that he/she will be deaf as well. If she has one blue eye, there is a good chance that she will be deaf in the ear on the side of the blue eye. 

As the name of the gene implies this is a dominant gene so if fully present its effects are produced (from genotype - the genetics to phenotype - the physical result). In a survey of 185 cats, one quarter had normal hearing and yellow eyes, 31% had normal hearing and blue eyes, 7% were deaf and had yellow eyes and 37% were deaf and had blue eyes. 

 The third and highly unusual genetic make-up that results in all-white cat coats is the albino. This is complicated genetically so a brief mention is probably best. There are alleles that are known to produce albinism. 

An allele is one member of a pair of genes at a certain point on the chromosome. The alleles concerned are blue-eyes albino, pink eyes albino, Burmese Pattern, Siamese Pattern and full color (ref: Sarah Hartwell). These cats have pink eyes. The all-white cat is more prone to contract skin cancer as the skin more readily absorbs ultraviolet light. This should be born in mind by keepers of white cats in hot climates. Source:
  • Messybeast
  • Robinson's Genetics
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