Genetics

A-locus

6. a^m - Mottled Agouti

The mottled agouti gene is a result of radiation experiments at Oak Ridge. It uncertain whether this gene is available for mouse fancier and if it is, where. (The author welcomes your feedback!) On the a-locus, a^m is lower than a^t and higher than a.

Like the viable yellow A^vy, mottled agouti gives widely varying phenotypes ranging from deep black, completely tanless mice that can't be told apart from extreme non-agouti a^e/a^e mice, through variable mottling of yellow/red and black to pseudoagouti (full agouti pattern). Again, like A^vy, the phenotype variation of the young is strongly influenced by the agouti locus genotype of the mother. Both homozygotes and heterozygotes with a (a^m/a) show variance in coloration.

It is quite interesting, that the two a-locus motting genes, A^vy and a^m can produce almost all possible a-locus derived phenotypes between the two genes, with pseudoagouti being the "common end": A^vy produces colours from all red through mottling to pseudoagouti, a^m produces colours from pseudoagouti to extreme black. As both genes can produce pseudoagouti, only breeding tests can show whether a pseudoagouti mouse is a A^vy or a a^m mouse. Of course, A^hvy can produce the whole of variation all by itself!

6.1. Homozygous Forms

As has been noted above, the phenotype of a^m/a^m can vary greatly. For a fancier, a^m can be useful in breeding a line of brindles, blacks and dilutions of these two varieties.

4.2. Heterozygous Forms

When a^m is heterozygous with any of the a-locus genes higher on the dominance scale, it does not show. Therefore, only useful heterozygous forms are a^m/a and a^m/a^e. These, however, have the same phenotype as homozygous a^m/ a^m.