The D Locus
The D Locus, also known as the Dilute or Russian Blue Locus, is responsible for the distribution of pigment in each strand of hair. The wildtype of this Locus is dominant and represented by “D”. Each strand of hairs’ pigment is distributed evenly throughout. The recessive mutation is represented by “d” and caused the pigment in each strand of hair to be clumped together in an uneven fashion. This causes the rat to be a dark blue colour that resembles Russian Blue cats. When the rat has no other mutations on the other loci and is Agouti based and is dominant on this locus, the colour is known as Agouti. When it is agouti based and has a recessive allele this locus, it is known as Russian Blue Agouti. When the rat is black based with a dominant allele on this locus, it is known as Black. When it has a recessive allele on this locus it is known as Russian Blue.
Alleles on the D locus are as follows:
D- Black
d- Russian Blue
DD and Dd animals will have normal pigment distribution, while dd animals will have uneven pigment distribution.
Russian Blue Irish Standard Ear
CLR Arae
Russian Blue Agouti Extreme Blaze Berkshire Dumbo