ch03 Student: If a phenotype is controlled by the genotypes at two different loci the interaction of these genes is called

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1 ch03 Student: 1. Which of the following is not a phenotypic description of allele interactions affecting the expression of traits? incomplete dominance codominance polymorphic multifactorial E. pleiotrophic 2. If a phenotype is controlled by the genotypes at two different loci the interaction of these genes is called epistasis. epigenetics. dominance. codominance. E. incomplete dominance. 3. What would be an explanation for the phenomenon where a cross of a purebred, female, red eyed fruit fly with a purebred male, white eyed fly resulted in a phenotypic ratio that has a significantly greater number of red eyed flies than would be predicted by using Mendel's laws? The red eye allele is dominant and sex linked. The white eye allele is dominant and sex linked The red eye allele is recessive and lethal The white eye allele is recesive and lethal E. male pattern baldness 4. What can explain the phenomenon where the same genotype might give rise to different phenotypes? pleiotropy codominance incomplete dominance complete dominance E. penetrance and expressivity

2 5. Which of the following phenotypic ratios show incomplete dominance? 2:1 3:1 1:2:1 1:1 E. 4:1 6. Which of the following ratios show codominance? 2:1 3:1 1:2:1 1:1 E. 4:1 7. Which of the following ratios indicates a lethal gene? 2:1 3:1 1:2:1 1:1 E. 4:1 8. The gene that controls ABO blood type phenotype demonstrate which of the following inheritance patterns? complete dominance. recessiveness. codominance. complete dominance, recessiveness, and codominance E. none of the choices is correct. 9. Which of the following ratios demonstrate gene interaction? 2:1 3:1 1:2:1 9:3:4 E. 1:3 10. If a gene is monomorphic in a population the most likely phenotypic ratio for the trait that would be obtained from a cross between two random individuals in the population would be 2:1 Cannot be predicted 1 3:1

3 11. The phenotypic ratio 2:1 may indicate complete dominance. codominance. epistasis. recessive lethal. E. codominance and epistasis only. 12. The phenotypic ratio 9:7 may indicate complete dominance. codominance. epistasis. recessive lethal. E. complementary gene action. 13. The phenotypic ratio 9:3:4 may indicate complete dominance. codominance. epistasis. recessive lethal. E. codominance and epistasis only. 14. Which ratio would indicate that a phenotype is controlled by multiple genes? 3:1 2:1 1:2:1 9:3:3:1. In rats, the allele for pigmentation (P) is dominant to the allele for albinism (p). The gene for black pigmentation (B) is dominant to the gene for cream pigmentation (b). If the dominant P allele is absent, gene B is inoperative.

4 15. Predict the genotypes and phenotypes of the F 1 progeny of a cross between a homozygous black rat and an albino homozygous for cream. PPBB, black PpBb, black PpBb, albino ppbb, albino 16. Predict the phenotypic ratio of the F 2 progeny of a parental cross between a homozygous black rat and an albino homozygous for cream. E. 1 albino : 2 black : 1 cream 9 black : 3 cream : 4 albino 9 black : 3 albino : 4 cream 12 black : 3 cream : 1 albino 12 black : 3 albino : 1 cream In the common daisy, the genes A/a and B/b represent two pairs of alleles acting on flower color. A and B are required for color. The alleles of these two genes show recessive epistasis. The two gene pairs together thus show duplicate recessive epistasis.

5 17. Predict the genotypes and phenotypes of the F 1 progeny of a cross between two colorless plants, one homozygous for A and the other homozygous for E. AAbb, colorless aabb, colorless AaBb, colored AaBb, colorless aabb, colored 18. Predict the phenotypic ratio of the F 2 progeny of a cross between two colorless plants, one homozygous for A and the other homozygous for 3 colored : 1 colorless 9 colored : 7 colorless 9 colorless : 7 colored 15 colorless : 1 colored E. 15 colored : 1 colorless

6 19. A certain disease is caused by homozygosity of the g allele (G is the corresponding wild-type allele). However, the penetrance of the disease is 75%. Two individuals known to be heterozygotes have a child. What is the probability that the child exhibits the disease? E. 1/4 3/4 1/8 3/16 9/ A number of interacting genes produce quantitative inheritance. The transmission of these genes can be seen in the phenotypical pattern of discontinuous distribution of discrete phenotypes. continuous variation in phenotypic expression. strict dominance and recessiveness. only discontinuous distribution of discrete phenotypes and continuous variation in phenotypic expression. 21. In some plants, a purple pigment is synthesized from a colorless precursor. In a cross between two parental plants, one purple and the other colorless, an F 1 generation was produced that was all purple. The F 2 produced from the F 1 had 775 purple, 200 red and 65 colorless plants. What mode of inheritance and phenotypic ratio do these results suggest? Incomplete dominance, 1:2:1 phenotype ratio Dominant epistasis, 12:3:1 phenotype ratio Codominance, 1:2:1 phenotype ratio Recessive epistasis, 9:3:4 phenotype ratio

7 1. D ch03 Key 2. A 3. D 4. E 5. C 6. C 7. A 8. D 9. D 10. C 11. D 12. E 13. C 14. D 15. B 16. B 17. C 18. B 19. D 20. B 21. B

8 ch03 Summary Category # of Questions Blooms: 1. Remember 4 Blooms: 2. Understand 2 Blooms: 3. Apply 13 Blooms: 4. Analyze 2 Hartwell - Chapter Learning Objective: Categorize allele interactions as completely dominant, incompletely dominant, or codominant. 4 Learning Objective: Recognize progeny ratios that imply the existence of recessive lethal alleles. 3 Learning Objective: Predict from the results of crosses whether a gene is polymorphic or monomorphic in a population. 1 Learning Objective: Conclude from the results of crosses whether a single gene or multiple genes control a trait. 2 Learning Objective: Infer from the results of crosses the existence of interactions between alleles of different genes includ ing complementation, epistasis, and redundancy. Learning Objective: Recognize when a given genotype in different individuals does not correspond to the same phenotyp e. Learning Objective: Explain how continuous traits, like human height and skin color, are controlled by multiple alleles of multiple genes. Section: Section: Topic: Extensions to Mendel for Multifactorial Inheritance 13 Topic: Extensions to Mendel for Single-Gene Inheritance

! Allele Interactions

Chapter 4!Extensions to Mendelian Genetics! Allele Interactions 1 INTRODUCTION Mendelian inheritance describes inheritance patterns that obey two laws Law of segregation Law of independent assortment Simple