Review the information on Labrador retrievers above.  What are the phenotypic ratios of the F1 generation offspring of two dihybrids? Make sure to match the numbers with coat colors (e.g, which number in the ration goes with which color).  Use a Punnett square to determine the ratios and show your work.  Make sure to state the phenotypic ratios.  Finally, what color are the parents?

As seen in the photo, Labradors come in three colors-- black, brown and yellow.  What is the genetic basis for these different coat colors?  One gene produces melanin, a pigment which is deposited in the dog's fur and makes the color dark.  With this gene, allele B (black) is dominant to allele b.  Only in the case of a recessive homozygote (bb) will the dog's phenotype be brown.  The regulatory gene is separate from the melanin gene but it acts as a switch, either turning the melanin gene on or turning it off.  Allele E is dominant and allows for the melanin to be deposited in the dog's fur ("on" switch), but if the switch gene is a recessive homozygote, the melanin is blocked ("off" switch) and a yellow dog is the result!

1. Review the information on Labrador retrievers above.  What are the phenotypic ratios of the F1 generation offspring of two dihybrids? Make sure to match the numbers with coat colors (e.g, which number in the ration goes with which color).  Use a Punnett square to determine the ratios and show your work.  Make sure to state the phenotypic ratios.  Finally, what color are the parents?