In genetics, the dash symbol (–) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, a– means the individual has either the genotype aa or aa. two genes that undergo independent assortment affect coat color in the house mouse. each gene has two alleles, one of which is dominant for coat color. genotypes of the form a– b– have a brownish color called agouti, those of the form a– bb are black, and those of the form aa b– and aa bb are albino (white). what ratio of agouti : black : white is expected from the cross aa bb × aa bb?