In mice, agouti fur is a dominant trait resulting in individual hairs having a light band of pigment on an otherwise dark hair shaft. A mouse with agouti fur is shown here, along with a mouse with solid color fur, which is the recessive phenotype (A = agouti; a = solid color).
A separate gene, which is not linked to the agouti gene, can result in either a dominant black pigment or a recessive brown pigment (B = black; b = brown).
A litter of mice from the mating of two agouti black parents includes offspring with the following fur colors:
* solid color, black
* solid color, brown (sometimes called chocolate)
* agouti black
* agouti brown (sometimes called cinnamon)
What would be the expected frequency of agouti brown offspring in the litter?