7. a - Nonagouti, Self

Nonagouti a is an old mutation, turning ticked agouti group colours into self. It is the second lowest recessive in the a-locus and is recessive to all the upper genes, but dominant over ae. Without the nonagouti gene, the mouse fancy would have gone nowhere near where it is today.

As its name implies, nonagouti removes all agouti-styled pattern from the hairs, that is - it removes yellow pigment. Nonagouti a animals still tend to have some (partialy or completely) yellow / tan hairs: usually behind the ears, in the vent and round the teats. There also tends to be some tan ticking along the flanks of the mouse. All of these are considered faults in mouse standards. As a doesn't remove the faulty tan hairs, it is up to the breeder to selectively breed her mice to be as self as possible, with as little yellow pigment as possible.

7.1. Homozygous Forms

a/a is found on black, chocolate, blue, lilac, dove, champagne, silver, siameses, himalayan, burmeses, bone, beige, nonagouti chinchillas (yes, this critter does exist, although it doesn't look anything like a chinchilla, but is a not-too-black black) and nonagouti marked varieties.

7.2. Heterozygous Forms

As a is such a low recessive in the a-locus, it's effects are hidden by Ay, Avy, Aw, A, at and am. It is also a full dominant over ae, so you can't see whether a mouse is a/a or a/ae.

All "big A gene varieties" (except for A/at tans), non-agouti tans and foxes can have one serving of a as well.