Cat fur color is affected by two genes. The B gene codes for fur color. The dominant allele (B) produces black fur (phenotype) and the recessive allele (b’) produces a cinnamon phenotype (when homozygous). The second gene (D) codes for the density of brown or black pigment. The dominant allele (D) allows for full deposition of the black pigments and the recessive allele (d) allows for lesser deposition of pigment (when homozygous), as coded for by the B or b gene. Black cats appear blue with less dense deposition and cinnamon cats appear fawn. If a black cat (Bb’Dd) is crossed with a blue cat (Bb’dd).
For the description above, the D gene is said to be ________ relative to the B gene.