Coat types

Body types



Merle rats seemed to disappear in the UK at one point, but imports in 2015/16 brought merle back to the UK fancy. Merle works on the mink gene, and causes uneven distribution of pigments in the coat, causing distinct spots in the coat. This can appear similar to the ‘patchy moults’ which are commonly associated […]


The roan gene, also known as husky or European husky, is responsible for the vast majority of worried “why has my rat changed colour?” threads (the remainder being the work of Siamese kittens moulting into their adult coat). This gene has not been scientifically described, but commonly it is given the ro (roan) symbol. The […]


The rat variety called chinchilla is genetically very unlike chinchilla in the mouse. In the mouse the chinchilla colouration is caused by a c-locus mutation, and the white belly either by separate spotting genes or a-locus mutations. In rats, the chinchilla situation is more complicated. The main part of the story is a spotting gene […]

H locus and friends

Most rat markings are created by mutations at the H-locus. The most distinctive is probably the hooded, but the full variety is quite amazing. Opinions on which alleles actually exist in the fancy at the moment differ, but some known alleles include:

H – Wild type, minimum white spotting. He – Quite extensive white spotting […]

Red eye dilute

The red eye dilute gene came over to the UK in the mid/late 80s, both from European imports and American imports. Although the gene is called red eye dilute, the eyes can often be dark enough to be mistaken for black. Alleles at this locus are:

R – Dominant wild type (so “no effect”). Normal […]

Pink eye dilute

Pink eye dilute is a very common colour in the UK, and is one of the colours that has been around since even before the fancy. Alleles at this locus are:

P – Dominant wild type (so “no effect”). Normal pigment. p – Recessive pink eye dilute gene. Black pigment is reduced to a pale […]

Minks and pearls

Mink rats seemed fairly uncomplicated until around 2000, when mink rats were imported to the UK from American lines. When these newcomers were mated with the existing minks, it became apparent we had two completely separate but similar looking genes in play. These are generally known as mink (or English mink), and American mink (or […]


There are two different blue genes in the fancy – British blue and Russian blue. Both are entirely separate genes, with the only similarity between the two being that they give a grey colouring that’s been named blue.

British blue is at the D (dilute) locus. The alleles at this locus are:

D – Dominant […]


Black eyed