Dihybrid Practice Problems

All problems below involve hamsters and involve crossing them for two traits (dihybridization). Use the following letters to represent Dominant and Recessive traits. Black Fur (B) is Dominant over Brown (b). Short fur (S) is dominant over Long (s).

Problem 1. A hamster that is homozygous for black, short fur is crossed with a hamster that is homozygous for brown, long fur. a. Show the genotypes of the two hamsters in this cross. ______X ______b. Show all possible gamete combinations for each hamster. ______, ______c. Show the genotypes of the F1 produced from these gametes ______d. Show the mating of two of the F1. ______X ______e. Show the possible gamete combinations of each F1 parent.

f. Show all genotypes of the F2 zygotes:

Problem 2 Show the mating of a hamster that is homozygous recessive for both coat color and coat length with one that is heterozygous for both color and length. a. Show the genotypes of the two hamsters in this cross. ______X ______b. Show all possible gamete combinations for each hamster. c. Show the genotypes of the F1 produced from these gametes d. Show the F1 phenotypic ratio: e. Show the F1 genotypic ratio:

Problem 3 If rough coat texture(R) is dominant to smooth coat texture (r), Show the cross of a hamster that is heterozygous for fur length but homozygous recessive for fur texture with one that is homozygous recessive for coat length and heterozygous for coat texture. a. Give the genotypes of the two parent hamsters (P1) ______X ______b. Using a Punnett square, predict the F1 phenotypic and genotypic ratios.