Cat genetics white spotting

My book on cat genetics (Robinson’s) tells me that there are three kinds of white spotting. Actually, it includes the all-white cat within cats described as having white spotting but, in this article, I will describe the following three types, (a) piebald spotting (b) gloving and (c) brisket spots and lockets. The pure white cat can be caused by the white spotting gene with maximum amount of white and the dominant white gene has the same effect.

Bicolor black and white Persian cat
Persian – “Oreo”. This cat has the classic bicolor coat caused by the presence of the piebald gene (white spotting gene). Image: copyright Helmi Flick.
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Piebald spotting

This is a reference to the piebald gene which is also known as the white spotting gene. My book tells me that the coat is tricoloured or bicoloured and that the coat is coloured except for a variable amount of white. Often you see the Turkish Van type Mediterranean cat under this heading because they have an inverted white V extending between the eyes, on either side of which you will see black markings or they might often be ginger markings. The Turkish Van is predominantly white. You can see this face in the third image down on the left-hand side.

You can grade the amount of white in cats affected by the white spotting gene (see the chart immediately below). The piebald spotting gene often causes the chest and stomach to be largely white and the lower parts of the legs are often white. In summary, the body shows various amounts of white. Sometimes the white areas are so extensive that the coloured areas are broken up into small patches.

The piebald gene creates bicolour cats and bicolour cats are very common in the world of cats. And in my view, the extent of white fur on the coat increases in warmer climates such as in countries around the Mediterranean as an adaption to the hot weather to better protect themselves.

When grading the effect of the piebald gene, you award grade 1 to a cat with very minimal amounts of white fur and at the other end of the scale, there is the white cat which is grade 10. If the cat is coloured, let’s say black, and there are some small patches of white on the cat’s back and perhaps one paw that cat would be graded as level 2 (low grade) on the scale of the variety of expression of the piebald white spotting gene.

A cat on level 5 of the variety expression would have a coat that is very typically bicolour with almost equal amounts of white fur and coloured fur.

Strange coat on a cat with the piebald gene

Is this real? It looks unreal! There are large areas of white and strange black markings. She is a bicoloured cat carrying the piebald gene.

Weird bicolour cat
Weird bicolour cat. Image in the public domain.

How the piebald gene creates white spotting

Robertson’s Genetics for Cat Breeders and Veterinarians (my go-to book on cat genetics which is poorly written ๐Ÿ™‚ ) explains how the piebald gene works. The white spotting gene or piebald gene is represented by the symbol S. It causes a defect in embryonic cells called melanoblasts which normally develop into melanocyte cells. These cells produce the dark brown pigment called ‘melanin’ which migrates into the hair strands.

The melanoblasts migrate from the neural crest along the back of the embryo to other parts of the body during the embryonic growth of the skin. However, if the melanoblast cells fail to get to their destination as dictated by the cat’s development, before the skin is formed the skin, it is then deficient in these pigment producing cells. The outcome, as you would expect, is that there is a lack of pigment producing melanocyte cells in the skin in certain places which means that the hair strands in those places don’t contain melanin pigment in which case they are white.

Variability

It is obviously clear from the charts above which are published here with my thanks to Sarah Hartwell, that the piebald gene expresses itself in a wide range of ways. It is very variable in how the gene is shown in the phenotype of the cat. And it is said that this is due to a combination of polygenes and perhaps “due to random eccentricities of individual development” in the elaborate language of my reference book.

The book tells me that white spotting may be due to more than simply the piebald gene. They say that “Multiple genes, such as one controlling low-level white spotting, may be present.”

Horses – a quick diversion

Just a quick note to remind ourselves that the piebald horse also called the painted horse has a coat which has been created by the piebald gene. The piebald horses a bicolour horse meaning white and another colour.

Gloving

This refers to white on the cat’s paws in recognition of gloves worn by people in cold weather. The white fur of the paws usually extends to a limited extent up the feet. A cat’s foot extends all the way up to the first major joint. This is the hock. The picture below shows you the location of the hock on a straightforward tabby cat and the part of the limb below (distal) the hock is the cat’s foot at the end of which are the cat’s paws on which the cat walks (digitigrade).

Domestic cat's hock a joint between the foot and lower leg
Domestic cat’s hock a joint between the foot and lower leg. Image: PoC.

On occasions there might be a little white on the face, belly and chest. Sometimes the Ragdoll cat has gloving and breeders work very hard at getting it right with a clean demarcation line between the white and coloured fur.

Angel a Ragdoll cat
Angel a Ragdoll cat

The paws are usually white gloves but the lower portions of the legs can be more extensively white which creates what breeders describe as “stockings” or “laces”. The breeders of Birman cats have refined the gloving of feet. An example can be seen in the picture below.

Birman cat by Helmi Flick
Birman cat by Helmi Flick

Brisket spots and lockets

You will see small white spots or streaks on the throat, stomach and chest. They are normally quite small except perhaps for a streak on the stomach. Some breeds have white toes within this category.

Below is an example of a random-bred cat with a locket. These cats are sometimes called tuxedo cats as well. Is not known whether a single gene causes lockets but it is presumed that it is caused by polygenetic inheritance.

Laura Lee's medium-longhaired tuxedo
Laura Lee’s medium-longhaired tuxedo. Screenshot from video.

Heredity

This believed that the heredity of white spotting was determined to be that of an incompletely dominant gene. In other words, there is a variability of expression of the gene and it might be expressed differently for animals with different genetic backgrounds.

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