Why does the dominant white gene cause deafness in some cats?

The dominant white gene in cats is associated with an increased risk of deafness. This is because the gene affects the development of the cells in the inner ear that are responsible for hearing.

All-white semi-feral cat. Image in public domain.

The dominant white gene can cause the cells in the inner ear to fail to develop normally, leading to a condition called congenital sensorineural deafness. This type of deafness is caused by damage to the hair cells in the inner ear, which are responsible for converting sound waves into electrical signals that are sent to the brain.

RELATED: What percentage of white cats are deaf?

Cats that have one or two copies of the dominant white gene are at an increased risk of developing congenital deafness. This is particularly common in cats with white fur and blue eyes, as the gene that causes blue eyes is closely linked to the dominant white gene.

RELATED: Deafness in cats – causes, diagnosis and management plus dog info. too

It is important to note that not all cats with the dominant white gene will be deaf, and not all deaf cats have the dominant white gene. Deafness can also be caused by other genetic mutations, environmental factors, or as a result of age-related hearing loss.

Is cat personality linked to coat colour and type?

People like to think that there is a connection between the appearance of someone or an animal and their personality. British people refer to tortoiseshell cats as being "naughty torties" or having "catitude". Sometimes blotched tabbies are referred to as "real homebodies". And mackerel tabbies are seen as being independent. While white patches on a cat's coat have a calming effect on the personality.

Incidentally, it is not until fairly recently that people started to understand that domestic cats have a personality. Even scientists believed that only humans had personalities. That seems hard to believe nowadays.

Is this tortie a naughty cat? Photo:Twitter.

I've always felt that red tabby cats have good relaxed characters. Red tabbies are also called ginger or marmalade cats. They always seem to be spoken of in glowing terms as companions with nice, affable characters. But this is all anecdotal. To turn to science, some scientists believe that the biochemistry that creates different coat colours and types also affects the cat's brain. This is called "pleiotropy". But apparently there is little evidence to support this scientific theory says Dr Bradshaw in Cat Sense.

Perhaps we are on a more solid scientific footing when we turn our attention to the purebred, pedigree cats. With pedigree cats there is a lineage so we know the parents and grandparents; in short, there is a family tree, which allows scientists to study the inheritance of the genes.

There is a relatively restricted gene pool in breeding lines which allows the temperament of a founding cat to be brought forward all the way down the breeding line. So, for example, there is a limited number of high-quality male cats within each breed who are available to produce the type of coat desired as per the breed standard. As a result, the personality of these tomcats becomes predominant within a section of all the cats in a single breed.

For example, there was a time about 20 years ago when British Shorthair cats bred in Scotland with tortoiseshell, cream and especially red coats were difficult to handle. They traced this personality trait back to a single male cat who had a difficult personality. This, incidentally, is an example of breeders breeding for appearance over personality. This founding, male cat was unsuitable, it seems.

And also pointed cats, which you will see both in the Siamese and other pedigree cats and indeed in non-pedigree cats, are likely to be vocal. This is a well-known trait for Siamese cats. The reason, it is said, is because the gene that causes the points i.e. the dark extremities to the cat's body are rare unless that cat has at least one Siamese in its recent ancestral past.

Another way in which coat type and colour can be linked to personality is when the gene that controls the coat is physically close, on the same chromosome, as the gene that affects the way the brain develops. Under these circumstances the chances that a kitten will inherit the combination of these two genes, one affecting the coat and one affecting the brain is much higher. They tend to be inherited together although it doesn't always happen.

An example would be the dominant white gene which causes a cat's coat to be devoid of pigment and therefore is white, sits next to a gene which causes both eyes to be blue and the cat to be deaf. That's why white cats are often deaf with blue eyes or they have odd-eye colour. Because the cat is deaf it affects their personality and therefore in this instance coat type and colour affects personality.

I am indebted to Dr John Bradshaw for the above. Some more...

One aspect of people attaching personality to coat type is that it may colour their opinion of their cat (excuse the pun). The point that I am getting at is that if a person believes that tortoiseshell cats are naughty and if with that belief, they mishandle their tortoiseshell cat and are scratched, the two aspects to their relationship come together which may result in the cat being relinquished to a shelter.

A study found that participants were likely to attribute friendliness to orange cats and intolerance to tricolour cats and aloofness to white and tricolour cats. White cats were seen as being more shy and calmer than cats of other colours.

The participants to the study said that they thought personality was more important than colour when selecting a cat companion. This is interesting because cat breeders of purebred cats attach more importance to appearance that personality. There appears to be a disconnect between cat breeders and their clients.

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. Photo: Reddit.com.

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

 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 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
• Me