The A Locus
The A locus, also called the Agouti Locus, is responsible for the banding of the fur. The wildtype of this Locus is dominant and is represented by “A”. Each strand of hair is banded in different colours, namely black and yellow. The recessive mutation of this locus is represented by “a”. Each strand of hair is a solid colour. When a rat has no other mutations on the other loci (is wildtype on all other loci) and has a dominant allele on this locus, the colour is known as Agouti. When it has a recessive allele on this locus, the colour is known as black.
Alleles on the A locus are as follows:
A- Banded (agouti based)
a- Non-Banded (self/solid) (black based)
AA and Aa animals will be agouti based, while aa animals will be black based.
Agouti Berkshire Standard Ear Doe
Black Unmarked Harley Standard Ear