Exam 2 Version B KEY

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Lehigh University *

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044

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Biology

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Dec 6, 2023

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docx

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Name________________ Version B Biology 044 – Fall 2023 – Exam 2 Name______________________________ You have worked hard so far this semester to engage with the course material. Try your best to relax and do your best. Before you begin: Make sure your exam has 6 pages other than this cover sheet (5 double-spaced pages and a blank page at the end for scrap work). Write your name on this test. Write your name, recitation day/time, and date on the bubble sheet. Additionally, bubble in the version of the test you have (above). Only your answers on the bubble sheet will be graded for the multiple choice. During the test: Write your answers in pen. Before you hand in your exam: Be sure to sign the honor code statement at the end, then hand in your answer sheet, question sheet, and scrap paper separately.

Name________________ Version B

Name________________ Version B Multiple choice questions (63 points total; Total number of questions: 16; Each question is worth 3.5 points) 1. Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago) and organisms colonized the island, the evolution of life on this new island should have been most strongly influenced by ________. a. habitat differentiation b. sexual selection c. founder effects d. a genetic bottleneck 2. Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility and death, usually from coronary artery disease, at an average age of 13 years. Patients who look very old even as children do not live to reproduce. Which of the following represents the most likely assumption? a. The disease is dominant. b. The disorder will increase in frequency in successive generations within a family. c. Each patient will have had at least one affected grandparent or parent. d. The disorder may be due to mutation in a single protein-coding gene.

Name________________ Version B 3. Which of the above graphs best represents the relationship between the potential intensity of directional selection and the genetic variation present within a population? a. Graph A b. Graph B c. Graph C d. Graph D 4. People with cystic fibrosis (CF) are homozygous recessive for mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. These mutations cause the CFTR protein to become dysfunctional, and it is unable to move chloride to the cell surface. Ultimately mucus can build up in organs, and in the lungs, the mucus clogs the airways and traps bacteria, leading to infections, inflammation, and respiratory failure. In a human population, if 9 in 10,000 newborn babies are born with CF, what are the expected frequencies of the dominant ( A 1 ) and recessive ( A 2 ) alleles according to the Hardy-Weinberg model in that population? a. p = 0.9800, q = 0.0200 b. p = 0.9997, q = 0.0003 c. p = 0.9604, q = 0.0392 d. p = 0.9700, q = 0.0300 e. p = 0.9600, q = 0.0400 5. Which of the following statements about the law of segregation is correct? a. It describes the inheritance of different genes relative to one another. b. It describes the inheritance of different alleles relative to one another. c. It suggests that all genes are inherited together as a single unit. d. It indicates that genes located close to each other on the same chromosome always segregate together.

Name________________ Version B 6. Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S , have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N , determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce ________. Note : True-breeding means that if the individual was to mate with itself, it would only ever produce offspring with the same phenotype as itself. a. all sharp-spined progeny b. 50 percent sharp-spined and 50 percent dull-spined progeny c. 25 percent sharp-spined, 50 percent dull-spined, and 25 percent spineless progeny d. all spineless progeny e. It is impossible to determine the phenotypes of the progeny. 7. The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid1700s. They do not marry members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations, including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population? a. Population bottleneck and Hardy-Weinberg equilibrium b. Heterozygote advantage and stabilizing selection c. Sexual selection and inbreeding depression d. Mutation and natural selection e. Founder effect, inbreeding, and genetic drift 8. Which of the following statements is TRUE about a phylogeny, as represented by a phylogenetic tree? I. Descendant groups (branches) from the same node do not share any derived traits. II. A monophyletic group can be properly based on convergent features. II. A polyphyletic group are most associated with divergent features a. Only I b. Only II c. Only III d. I, II, and III e. None; not I, II, or III

Name________________ Version B 9. There is a locus that has two different alleles, allele A and allele B. In each of the above graphs, we have plotted the difference in the selection coefficient for allele A and the selection coefficient for allele B on the Y axis against the frequency of Allele A (graph is plotted from allele frequency of 0 to allele frequency of 1). Which graph would be consistent with negative frequency dependent selection at this locus? a. Graph A b. Graph B c. Graph C 10.If the selection coefficient for the heterozygote genotype at a given locus is distinct from those of both homozygous genotypes, the locus is not characterized by complete dominance. a. True b. False 11.Which of the following is the most predictable outcome of increased gene flow between two populations? a. Lower average fitness in both populations b. Higher average fitness in both populations c. Increased genetic difference between the two populations d. Decreased genetic difference between the two populations e. Increased genetic drift

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