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 […]

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

Burmese & black eyed

These genes only show their effects on rats who already have a combination of the albino, Himalayan, and/or marten alleles on the c locus. Although the black eyed gene has been scientifically described, the Burmese gene hasn’t as of yet. The idea that these two genes are allelic is a fairly new idea, but it […]

C locus

Known as the Colour locus, hence the symbol C. This is also sometimes referred to as the albino locus. Alleles at this locus are:

C – Dominant wild type (so “no effect”) ch – Himalayan, an acromelanistic pattern – pigment only appears depending on the temperature, so the cooler parts of the animal are coloured. […]


Officially known as brown (hence it being the B locus), we tend to call the effects of this gene chocolate in rats. It’s a fairly old gene, first being described by Castle and King in 1932. The alleles at this locus are:

B – Dominant wild type (so “no effect”) b – Recessive brown gene. […]