Colour genes

Marking genes

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. In rats this is the face, ears, tail, and feet. Eyes are red to ruby.
  • cm – Marten. Yellow pigment is almost entirely removed and becomes silver or very pale yellow. Black pigment is normal in babies, and a charcoal grey in adults. Eyes are pink to red.
  • c – Albino. No pigment is expressed at all, so fur remains entirely white, and eyes are bright pink.

The wild type allele is dominant to all others here, but the other three alleles are all codominant. With Siamese, Himalayan, and albino, it doesn’t matter if the rat is agouti or non-agouti based (A- or aa), the look of the rat will be the same – for these varieties it is not important whether the rat is agouti based or not.

aaCC, aaCc, aaCch, or aaCcm: Full colour black.

chch: Siamese

chc: Himalayan

cc: Albino

aacmcm: Marten