Let's start with the A locus. Genes within the A locus don't change the color of the hair, but instead affect the arrangement of color pigments. There are three possible genes in this locus:

  (A) - agouti/chestnut (wild type)
  (a^t) - tan/otter
  (a) - self

Chestnut (AA, Aat, Aa)	Otter (atat, ata)	Self (aa)

The Wild Pattern - Chestnut Agouti

A

The agouti pattern, also called chestnut agouti or just plainly chestnut, is the wild rabbit pattern. It’s a lovely interplay of black and yellow pigments in their original form. The (A) gene is completely dominant, so no matter what the second gene is at the A locus, an (A) will override all the effects of the other gene.

If you look closely at the fur, you will see that each hair contains rings of colors that create the beautiful ticking pattern seen in chestnuts. The hair closest to the skin is a gray or slate blue, followed by yellow, and then followed by black on the tips of the fur. Chestnut rabbits will also have light cream to white markings on their undersides: the belly, chin, inside of the legs, and bottom of the tail.

There are several variations of the agouti pattern. Common varieties of agouti-color rabbits include chestnut agouti/castor, opal (blue), chocolate agouti/amber and lynx (lilac). You can see this color difference when the kits are born, however they may be mistaken for otters before their fur starts to grow.

Otters & Martens

a^t

The second gene of this set is the tan pattern, or otter, symbolized by the (a^t) gene. The distinctive tan pattern produces a solid color over the back and sides. Like agouti, rabbits with the tan pattern will have light cream to white markings on their undersides. They will also have markings in the ears, the neck triangle, and intermingled coloration on the chest and dewlap.

The Simple Self Gene

a

The third, and the most recessive gene in the A locus is the self gene - (a). Any rabbit that shows a self color has the genotype of (aa), because it cannot hide agouti or tan pattern under it as it removes all banding.

Let's not be confused with the word “self” in the show world, which means one single color all over like black, blue, chocolate, and lilac. When we’re talking genetics, the definition is slightly different. In addition to black, blue, chocolate, and lilac, self colors also include tortoise, siamese sable, sable point, smoke pearl and other unrecognized varieties.