In Labrador retrievers, coat color is determined by two sets of genes on different loci [LOH-sy]. At one locus, the upper case B allele [uh-LEEL] codes for black coat color, and the lower case b allele codes for brown coat pigment. At the second locus, the upper case E allele codes for the presence of a transporter to carry pigment to the hair shaft and the lower case e allele codes for the absence of the transporter. In the presence of transporter, the dog is black or brown; in the absence of transporter, the dog is yellow. What is the genotype of a yellow dog that is heterozygous for the brown allele?