Colour genes

Marking genes

Roan

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 alleles at this locus are:

  • Ro – dominant wild type allele, so “no effect”.
  • ro – recessive roan allele. The rat has white markings on the stomach and face. From the first moult onwards the fur roans to white, gradually becoming more and more roaned until the rat is almost solid white.

The amount of white spotting on a roan is also dependent on the H locus genes involved. A self, Irish, or low white Berkshire with the roan gene would tend to be a roan (or “full roan”). A hooded or variegated type may end up being closer to a striped roan. A capped or similarly marked rat would likely end up being closer to a cap-stripe roan.