Bio 97, Section C, Midterm # 1, Fall 2015, Version A Oct 23, 2015 Note: some of the questions are labelled “mark all that may apply”. For those questions, you must mark all of the correct answers in order to receive crediIf you want to learn more check out bio 358 stony brook
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t for the question. There is no partial credit given for any question. Please pay attention to the fact that di↵erent questions are worth di↵erent numbers of points. 11. 1 point What do the F1 progeny of a cross between true-breeding, diploid strains di↵ering by a single trait tell you? (a) It helps determine the genotype of an unknown individual (b) It demonstrates the law of independent assortment (c) It tells you which trait is dominant and which is recessive. (d) It tells you that the trait is autosomal or sex-linked 2. 1 point Which of the following is not a classic “Mendelian ratio” (a) 9:7 (b) 3:1 (c) 9:3:3:1 (d) 1:2:1 3. (XX points) A couple has five children. What is the probability that exactly two are boys and three are girls? A.) 10/32 B.) 1/32 C.) 1/4 D.) 1/2 1 point4. 2 points Consider a cross, and its reciprocal cross, involving a recessive trait and true-breeding parental strains. If the male F1 progeny are only mutant when the mother comes from the true-breeding recessive strain, this is an example of: (a) Incomplete dominance (b) Epistatis (c) Partial linkage (d) Sex linkage 5. 1 point What is one cause of phenotypic mosaicism in female placental mammals? (a) Random X-chromosome inactivation revealing recessive mutations in a subset of tissues. (b) Trisomies of the X chromosome (c) An XXY karyotype (d) None of the above 6. 1 point What is the main outcome of meiosis? (a) Four daughter cells with half the ploidy of the somatic tissue (b) Four daughter cells with the same ploidy as the somatic tissue (c) Two daughter cells with half the ploidy of the somatic tissue (d) Two daughter cells with the sample ploidy of the somatic tissue 7. 1 point Mutations at mitotic cell cycle checkpoints may result in which of the following: (a) Two daughter cells with the same ploidy as the parental cell (b) Non-independent assortment of alleles (c) Somatic tissue with di↵erent genotypes (”genetic mosaic-ism”) (d) Unregulated cell growth leading to cancer 8. 1 point You have two true-breeding stocks of mutant Smurfs. One stock is pale blue in color, the other is completely white. Both traits are recessive to the wild-type dark blue, are due to mutations in di↵erent genes, and show no evidence of sex-linkage. You do the following experiment: First, you cross these two strains to one another. What is the phenotype of this F1 smurf? (a) white (b) pale blue (c) dark blue (wild-type) (d) translucent. 9. 2 points You then take these F1 individuals, and inbreed them, creating an F2 generation of Smurfs. You observe that some of these Smurfs are completely white. A series of test crosses reveals that some of these white F2 Smurfs are homozygous for the recessive allele at both genes. Assuming a linear pathway, which gene is the upstream gene (e.g., the first to act) in the Smurf pigmentation pathway: (a) the pale blue gene (b) the white gene (c) both genes act independently of one another (d) it is not possible to determine the order of gene action. 10. (2 points) The pathway for methionine biosynthesis is shown below: 1 2 3 4 homoserine cysteine cystathionine homocysteine methionine After performing an X-ray mutagenesis experiment on Neurospora crassa you find that one of your strains will no longer grow on media unless it contains methionine. However, to your surprise, you observe a buildup of cysteine in this mutant, this suggests that the mutant is a (mark all that may apply)? A.) Cysteine auxotroph B.) Prototroph C.) Mutant at step 2 D.) Mutant at step 4 and one or both of steps 2 and 3. 11. (2 points) Consider the following pedigree:I. II. III. 1 2 ? What does the pattern of disease transmission between generations I and II suggest? A.) The disease is X-linked recessive B.) The disease is an autosomal recessive C.) The disease is X-linked dominant D.) The disease is autosomal dominant 12. (1 point) What is the most likely genotype of the female labelled with a 2? A.) She is homozygous for the disease allele B.) She is homozygous for the dominant (non-disease-causing) allele C.) She is homozygous for the disease allele and nonpenetrant D.) She is a carrier 13. (1 point) What is the probability that the male labelled with a question mark (“?”) is a carrier? A.) 1/4 B.) 1/2 C.) 2/3 D.) 1 14. (1 point) You cross a true-breeding strain of green-feathered, yellow-beaked finches to a true-breeding straing of purple-feathered, black-beaked finches and obtain F1 progeny that are all green-feathered and black-beaked. Inbreeding the F1 gives 907 green-feathered, black-beaked : 295 purple-feathered, black-beaked : 310 green-feathered, yellow-beaked progeny. What can you conclude from this cross: A.) Green-feathers and yellow beaks are recessive B.) The feather and beak color genes assort independently and the purple-feathered/yellow-beaked double-recessive genotype is lethal C.) The feather and beak color genes are 25cM apart and the purple-feathered/yellow-beaked double recessive genotype is lethal D.) There is an epistatic interaction (dominant suppression) between the feather and beak color genes. 15. (1 point) What is a test cross useful for? A.) Destimining how many genes are contributing to a trait. B.) Determining the genotype of an individual. C.) Determining whether a phenotype is dominant or recessive. D.) Testing for complementation between two mutations.16. 2 points Two pure-breeding mutant plants produce white flowers. When they are crossed, all of the progeny have wild-type purple flowers. What does this genetic complementation tell you? (a) The two parental strains are mutant at di↵erent genes. (b) The allele exhibits incomplete dominance. (c) The allele is pleiotropic. (d) The two lines exhibit di↵erent mutations in the same gene. 17. 3 points You perform a cross involving two traits, A and B. For each, trait, there is a dominant and a recessive allele. You may assume that the lower-case letter represents the recessive. After inbreeding the F1 generation and counting phenotypes, you obtain the following results: AABB x aabb AaBb 41 64 A-B 7 64 A-bb 7 64 aaB 9 64 aabb What is the most best interpretation of the data? (a) Some of the progeny must be inviable/lethal (b) There is epistasis between the A and B genes (c) Genes A and B do not assort independently. (d) The two alleles of each locus to not segregate independently. 18. (1 point) When doing interrupted mating analysis in bacteria you observe that each Hfr strain transfers genes to the recipient in a replicable but distinctly unique sequence with respect to time. Which of the following is a reason for this: A.) The gene transfer start location is random B.) There are multiple insertion sequence (IS) elements on a bacterial chromosome C.) The orientation of the inserted F factor also impacts the order to gene transfer D.) both B and C are true 19. 1 point Consider a tri-hybrid genotype, AaBbCc generated by a cross involving true breeding recessive and true breeding dominant strains (AABBCC x aabbcc). If genes A and B are 10cM apart, and another 20cM separate genes B and C, what proportion of the tri-hybdrid’s gametes will be Abc? Hint: you may assume that crossovers between di↵erent pairs of loci happen independently. (a) 0% (b) 4% (c) 8% (d) 50%20. 1 point What proportion of the tri-hybrid’s gametes will be aBc? Hint: you may assume that crossovers between di↵erent pairs of loci happen independently. (a) 0% (b) 1% (c) 5% (d) 10% 21. (1 point) You have isolated a series of bacteriophage mutants m1, m2, m3, and m4. All mutants fail to complement one another, showing mutant phenotype m. In a series of co-infection experiments, you retrieve the following phenotypes (m+ = plaque-forming, m = unable to form a plaque): Cross Mutant phenotypes m1 x m2 Mostly m, some m+ m1 x m3 Mostly m, some m+ m1 x m4 Mostly m, some m+ m2 x m3 All m m2 x m4 All m m3 x m4 All m How do you explain these results? A. m1 is a deletion of the region containing the m3 and m4 mutations B. m1 is a deletion of the region containing the m2 and m3 mutations C. m2 and m3 are both deletions of the m4 region D. Mutations m2 and m3 are in a di↵erent gene than m1 and m4