Incomplete Dominance and Co-Dominance Practice Problems

Name ___________________________________Date____________________Pd________ Incomplete Dominance and Co-Dominance Practice Problems Incomplete Dominance 1. Coat color in mice is incompletely dominant. Yellow and white-colored mice are homozygous, while cream-colored mice are heterozygous. If two cream-colored mice mate, what phenotypic ratio can we expect of their offspring? Show the Punnett Square. Y W 1:2:1 Y YY YW W YW WW 2. In radishes, red and white are pure-breeding colors, while hybrids are purple. If a red radish is crossed with a white radish, what will be the phenotype of the F2 generation (assuming the F1 generation self-pollinates)? Show the Punnett Square. W R R R 25% Red R W RW RW RR RW 50% Purple W RW RW W RW WW 25% White 3. In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red (R) and white (W). The heterozygous genotype is expressed as pink. a) What is the phenotype of a plant with the genotype RR? ___________ Red b) What is the phenotype of a plant with the genotype WW? _ ______White c) What is the phenotype of a plant with the genotype RW? __ ______ Pink 4. A pink-flowered plant is crossed with a white-flowered plant. Show the Punnett Square. What is 50 the probability of producing a pink-flowered plant? _ __% R W W RW WW W RW WW 5. What cross will produce the most pink-flowered plants? Show a punnett square to support your RR * WW answer. R R 100% are RW (pink flowered) W RW RW W RW RW 6. In Andalusian fowls, black individuals (B) and white individuals (W) are homozygous. A homozygous black bird is crossed with a homozygous white bird. The offspring are all bluishgray. Show the cross as well as the genotypes and phenotypes of the parents and offspring. B B W BW BW W BW BW Parents: BB (black) * WW (white) Offspring: BW (gray) 7. What are the genotypic and phenotypic ratios if a black individual is crossed with a bluishgray individual? Show the Punnett Square. B B Genotype: 2:2:0 B BB BB W BW BW Phenotype: 2:2:0 Name ___________________________________Date____________________Pd________ 8. If two bluish-gray individuals were crossed, what would be the ratios for both phenotype and genotype of the offspring? Show the Punnett Square. B B W BB BW BW WW Genotype: 1:2:1 W Phenotype: 1:2:1 Co-dominance 9. In some chickens, the gene for feather color is controlled by codominance. The allele for black is B and the allele for white is W. The heterozygous phenotype is known as erminette (black and white spotted). BB a) What is the genotype for black chickens? __ _ WW b) What is the genotype for white chickens? _ BW c) What is the genotype for erminette chickens? ____ B 10. Two erminette chickens were crossed. Show the Punnett square. a) What’s the probability they would have a black chick? _ _% b) What’s the probability they would have a white chick? _ __% B 25 25 W W BB BW BW WW 11. A black chicken and a white chicken are crossed. Show the Punnett Square. What is the probability that they will have erminette chicks? _ _% 100 W B B BW BW BW W BW 12. In shorthorn cattle, when a red bull (RR) is crossed with a white cow (WW), all the offspring are roan—a spotted, red and white or milky red color. What offspring are expected from mating a roan bull and a roan cow? Show the Punnett Square. R W RR RW W RW WW R 25% red 50% roan 25% white 13. What phenotypes would you expect from a cross between a red bull and a white cow? Show the Punnett Square. W R R RW RW W RW All offspring= roan RW 14. If a roan bull were crossed with a red cow, what would be the possible phenotypes of their offspring? Show the Punnett Square. R W R RR RW R RR RW 50% red 50% roan