Monohybrid & Dihybrid Practice Problems Name:
Date:
1. In dogs, wire hair (S) is dominant to smooth (s). In a cross of a homozygous wire-haired dog with a smooth-haired dog, what will be the phenotype of the F1 generation?
What would be the genotype?
2. The ability to curl your tongue up on the sides (T, tongue rolling) is dominant to not being able to roll your tongue. A woman who can roll her tongue marries a man who cannot. Their first child has his father's phenotype. What are the genotypes of the mother, father, and child?
What is the probability that a second child won't be a tongue roller?
3. Woodrats are medium sized rodents with lots of interesting behaviors. You may know of them as packrats. Let's assume that the trait of bringing home shiny objects (H) is dominant to the trait of carrying home only dull objects (h). Suppose two heterozygous individuals are crossed. How many of each genotype would be expected if only 4 offspring were produced?
4. The common grackle is a species of robin-sized blackbirds that are fairly common (hence the name) over most of the United States. Suppose that long tails (L) were dominant to short tails in these birds. A female short-tailed grackle mates with a male long-tailed grackle that had one parent with a long tail and one parent with a short tail. What is the male's genotype?
5. Saguaro cacti are very tall cylindrical plants that usually have two L-shaped arms, one on each side. Suppose you lived in southern Arizona where the Saguaro cactus is common and you happen to have one growing in your yard. Your Saguaro has two arms but one is longer than the other. Now, assume that arm lengths in these cacti are controlled by a single gene with arms of the same length (A) being dominant to arms of different lengths. What is the genotype of your cactus?
6. Wolves are sometimes observed to have black coats and blue eyes. Assume that these traits are controlled by single genes and are located on different chromosomes. Assume further that normal coat color (N) is dominant to black (n) and brown eyes (B) are dominant to blue (b). Suppose the alpha male and alpha female of a pack (these are the dominant individuals who do most of the breeding) are black with blue eyes and normal colored with brown eyes, respectively. What are the possible phenotypes of their offspring?
7. Carrion beetles lay their eggs in dead animals and then bury them in the ground until they hatch. Assume that the preference for fresh meat (F) is dominant to the preference for rotted meat and that the tendency to bury the meat shallow (S) is dominant to the tendency to bury the meat deep. Suppose a female carrion beetle homozygous dominant for both traits mates with a male homozygous recessive for both traits. What will be the genotype of the F1 generation?