Dihybrid Practice

  1. A fruit fly with a genotype MmOo is mated with an identical fly. Use a dihybrid cross to show the genotype possibilities of their offspring.
  2. In guinea pigs, black fur (B) is dominant over white (b), and rough coat (R) is dominant over smooth (r). If a fully heterozygous black rough guinea pig is mated to a black rough animal that is also fully heterozygous, what is the chance that they will produce a white, smooth-coated guinea pig?
  3. Tall tomato plants are produced by the action of a dominant allele (T) and dwarf plants by its recessive allele (t). Hairy stems are produced by a dominant gene (H) and hairless stems by its recessive allele (h). A fully hetrozygous, tall, hairy plant is crossed with a dwarf hairless tomato plant. Determine the phenotypic ratio for the F1 generation.
  4. Black coat color in Cocker Spaniels is dominant, while red coat color is recessive; solid pattern is dominant, while spotted pattern is recessive. A solid black male is mated to a solid red female and produces a litter of six pups: two solid black, two solid red, one black and white, and one red and white. Determine the genotypes of the parents.
  5. In tomatoes, red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t). A plant that is RrTT is crossed with a plant that is rrTt. What are the chances of an offspring being heterozygous for both traits?