Dihybrid Cross Set #1 Practice ProblemsNAME:______
1. About 70% of Americans perceive a bitter taste from the chemical phenylthiocarbamide (PTC). The ability to taste this chemical is a results of a dominant allele (T) and not being able to taste PTC is the result of having two recessive alleles (t). Normal pigmentation is dominant (A) and the lack of pigment causing albino coloration is recessive (a). Complete the following Punnett square for a heterozygous normally pigmented woman who cannot taste PTC mates with a homozygous, normally pigmented man who is heterozygous for tasting PTC.
CROSS: ______x______
a. What are the possible genotypes of their children?______
b. What percentage of children will be albinos?______
c. What percentage of children will be non-tasters of PTC?______
2. A normal coat color (B) for a wolf is dominant to black (b) and brown eyes (E) are dominant to blue (e). Suppose the alpha male of a pack is black with blue eyes and the alpha female of the pack is normal in color and has brown eyes (heterozygous for both traits). Complete the following Punnett square for a cross between these two wolves and answer the questions to follow. CROSS: ______x______
a. What percent of the offspring will be normal in color with blue eyes?______
b. What percent of the offspring will be black with blue eyes?______
c. What percent of the offspring will be normal in color with brown eyes?______
d. What percent of the offspring will be black with brown eyes?______
3. In the breeding season, male Anole lizards court females by bobbing their heads up and down while displaying colorful throat patch. A male lizard that is heterozygous for bobbing his head and homozygous for the red throat patch mates with a female that is heterozygous for bobbing her head and homozygous recessive for a yellow throat patch.
CROSS: ______x______
a. What percentage of the offspring will bob their heads and have a red throat patch?______
b. What percent of the offspring will lack matches because they do not bob and have a yellow throat patch?______
c. What percentage of the offspring will have trouble finding mates because they lack on of the dominant traits?______
3. Carrion beetles lay their eggs in dead animals because and then bury them in the ground until they hatch. Assume that the preference for fresh meat (R) is dominant to the preference for rotted meat (r) and that the tendency to bury the meat shallow (D) is dominant to bury the meat far below the surface (d). Suppose a female carrion beetle is homozygous dominant for both traits mates with a male that is homozygous recessive for both traits.
CROSS: ______x______
a. What is the genotypic ratio for the F1 generation?
b. What is the phenotypic ratio for the F1 generation?