General Genetics, Exam 1 Example with Answers

Name_________________________________________ Exam 1 This examination is worth 100 points. There are 21 questions on 7 pages. Read through the questions completely before answering the questions. If you are unclear about a question, please ask me. Show all of your work for workout problems. Part A: Multiple Choice: Answer with the best choice. Make sure that you clearly circle the correct answer and erase any erroneous marks. (3.5 pts each) 1. An alternative form of a single gene is known as a(n): A. parental B. Dominant C. allele D. genotype E. recipricoal 2. The observable characteristics of an organism are called its ___________. A. phenotype B. genotype C. dominance D. genes E. none of the answers are correct 2. Which of the following would contain genetic material that is 100% identical? A. homologous chromosomes B. non-sister chromatids C. sister chromatids D. X and Y chromosomes E. independently assorting genes 3. In an animal with three pairs of chromosomes, assume that chromosomes 1,2, and 3 have come from the father, and 1’, 2’ and 3’ have come from the mother. In what proportion of the germ cells of this animal will all the paternal chromosomes be present together? A. 1/2 B. 1/4 C. 1/8 D. 1/16 E. 1/64 4. In Drosophila, the bobbed gene is located on the X chromosome and mutants have reduced bristle size (b). Unlike most X-linked genes, however, the Y chromosome also carries a bobbed gene. Suppose a bobbed male is mated to a wild type female (assume pure breeding stocks). What will be the appearance of the F1 offspring? A. all bobbed B. bobbed males; wild type females C. wild type males; bobbed females D. ½ bobbed and wild type males; all wild type females E. all wild type 5. In poultry, sex is determined by the ZW rather than the XY system. A dominant sexlinked gene (B) produces barred feathers, and the recessive allele (b), when homozygous produces nonbarred feathers. Suppose a nonbarred male is crossed with a barred female. What will be the appearance of the F1 birds? A. all barred B. barred males; nonbarred females C. nonbarred males; barred females D. ½ barred and unbarred males; ½ barred and unbarred females E. all nonbarred 6. When mapping three genes we need to remember to take into account _______________ crossover events _____________ time(s) in order to calculate the actual distance between the two genes that are furthest apart. A. single, 2 B. single, 1 C. double, 2 D. double, 1 7. Mendel's work with two-factor crosses led directly to which of the following? A. chromosomal theory of inheritance B. particulate theory of inheritance C. law of segregation D. law of independent assortment E. theory of biological evolution 8. A farmer crosses a yellow feathered hen with a red feathered cock and observes that all their offspring have orange feathers. If feather color is determined by a single gene, then what is the most likely explanation for these results? A. sex linkage B. Co-dominance of red and yellow traits 2 C. Incomplete dominance of red and yellow traits D. Overdominance of red trait E. Temperature-sensitivity of the red trait 9. The coat characteristics of Siamese cats and Himalayan rabbits, where proteins in the extremities function differently than in other parts of the body, is an example of A. incomplete dominance B. multiple allele systems C. semilethal alleles D. temperature-sensitive conditional allele E. none of the answers are correct 10. In human blood groups, the fact that an individual can have an AB blood type is an example of ___________. A. incomplete dominance B. blending C. heterozygote advantage D. temperature-sensitive conditional allele E. codominance 11. Sickle-cell anemia in humans is an example of ________________. A. incomplete dominance B. blending C. heterozygote advantage D. temperature-sensitive conditional allele E. codominance 12. In crossing two heterozygotes for a certain trait, one observes a 1:2:1 genotypic and phenotypic ratio. What is the most likely explanation for these results? A. incomplete dominance B. codominance C. heterozygote advantage D. semi-lethality E. both A and B 13. Among the Dihybrid crosses below, which will give a 1:1 ratio? A. AAbb x aaBB B. AaBb x aabb C. AaBB x aaBB 3 D. AABB x aabb E. AaBb x AaBb 14. For this question, choose the appropriate order for the following events. 1. metaphase 2. prometaphase 3. telophase 4. anaphase 5. prophase A. 3→4→1→2→5 B. 1→3→4→2→5 C. 2→5→3→4→1 D. 5→2→1→4→3 Respond with True or False to the following statements. If false, fix the statement. (3.5 pts each) 15. In humans, spermatogenesis and oogenesis results in the generation of four equal haploid cells from the original cell. 16. Both the Law of Segregation and the Law of Independent Assortment occur during Meiosis 1. PART B - Short answer and problem solving (be sure to show work for partial credit) 17. In a paternity dispute, it has come to light that the mother of the child has type A blood, the presumed father has type AB blood, and the child in question has type O blood. Answer yes or no to the following questions: A. Is it possible to rule out whether the presumed father is truly the biological father? Explain your reasoning? (5 pts) 4 B. In an emergency, can the mother provide a transfusion of blood to her child? Explain your reasoning? (5 pts) 18. Human cells normally have 46 chromosomes. For each of the following stages, state the number of chromosomes and chromatids present in a human cell. (In your answers, count chromatids that have separated from their centromere as a chromatid and a chromosome)(2 pts each answer). A. Prophase of mitosis: chromosomes ___________ chromatids ___________ B. Metaphase II of meiosis: chromosomes ___________ chromatids ___________ 19. The gene for white spots in the Chinese hamster is dominant to no spots. When two hamsters with white spots are crossed, 2/3 of the offspring possess white spots and 1/3 have no spots. What explanation can you give for the observed ratio (7 pts) 5 20. Below is a pedigree for the human trait “cromagnum forehead”. Answer the questions below the pedigree. a. What is the mode of inheritance? (3 pts) b. What is the genotype of individual 1? (2 pt) c. What is the genotype of individual 2? (2 pt) d. What are the possible genotypes and phenotypes of offspring if cousins 1 and 2 mated? (3 pts) 6 21. In Drosophila, the X-linked mutations, v (vermilion eyes), s (sable body color), and sd (scalloped wings), are recessive to the wild type genes. The table below lists the F1 offspring resulting from a testcross of a female heterozygote for all three genes. 110 320 1130 12 140 8 410 1245 vermillion vermillion, sable, scalloped vermillion, scalloped scalloped sable, scalloped vermillion, sable wild type sable A) Draw the linkage map for the parental female heterozygote without recombination distances.(5 pts) B) Explain what it means if we say that the coefficient of interference was 0.5 in this experiment? How would it affect the data if there was no interference?(4 pts) 7 Answers: 1. C 2. A 2. C 3. C 4. E 5. B 6. C 7. D 8. C 9. D 10. E 11. C 12. E 13. C 14. D 15. False, oogenesis gives unequal haploid cells (only 1 fertilizable) 16. T 17. A. Yes, father has no i allele to contribute to child B. No, type O is universal donor so can only accept blood from other O types 18. A. chromosomes= 46 chromatids= 92 B. chromosomes= 23 chromatids= 46 19. homozygous for white spots is lethal 20. A. autosomal recessive or sex-linked recessive (both are consistent with the pedigree) B. Cc heterozygous C. cc homozygous recessive D. ½ Cc normal forehead or ½ cc cromagnum head 21. A. s+____v____sd s____v+____sd+ B. should have observed 2x the number of double crossover (DCO) individuals Without interference, you should observe 40 DCO individuals 8