Question: In rats, gene B produces black coat color if the genotype is B-, but black pigment is not produced if the genotype is bb. At an independent locus, gene D produces yellow pigment if the genotype is D-, but no pigment is produced when the genotype is dd. Production of both pigments results in brown coat color. If neither pigment is produced, coat color is cream. Determine the genotypes of parents of litters with the following phenotype distributions:

1) 4 brown, 4 black, 4 yellow, 4 cream (ex: BBDD and BbDd)

2) 3 brown, 3 yellow, 1 black, 1 cream (ex: BBDD and BbDd)

3) 9 black, 7 brown

At the B locus, both parents were BB. At the D locus, both parents were Dd.
At the B locus, one parent was BB and the other parent could have had any genotype (BB, Bb, or bb). At the D locus, one parent was Dd and the other was dd.
At the B locus, both parents were BB. At the D locus, one parent was Dd and the other was dd.
At the B locus, one parent was BB and the other parent could have had any genotype (BB, Bb, or bb). At the D locus, both parents were Dd.