In Labrador retrievers, two genes control coat colour. At the first locus, the dominant allele B B\,B produces black pigment, while the recessive allele b b\,b produces brown pigment. At a second locus, the dominant allele E E\,E allows pigment deposition in the hair, whereas the homozygous recessive genotype ee ee\,ee prevents pigment deposition, resulting in a yellow coat regardless of the genotype at the first locus (recessive epistasis). The two genes assort independently.
A breeder crosses a black Labrador with the genotype BbEe BbEe\,BbEe with a yellow Labrador with the genotype BbeeBbeeBbee.
What is the expected phenotypic ratio of black to brown to yellow offspring from this cross?
9:3:49 : 3 : 49:3:4
3:1:43 : 1 : 43:1:4
1:1:21 : 1 : 21:1:2
3:3:23 : 3 : 23:3:2