exam 2_Fall_2023_KEY

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May 3, 2024

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Biology 3040 Exam 2 Name 1
Multiple Choice (4 pts each) 1. Which of the five marks in the tree above corresponds to the most recent common ancestor of a mushroom and a fern? B 2. The ratio of the rate of nonsynonymous to synonymous mutations ( k A /k s ) is less to one if a gene is evolving ______. A k A /k s ratio greater than one indicates that the gene is evolving _______. a. neutrally; under purifying selection b. under positive selection; neutrally c. neutrally; under positive selection d. under purifying selection; neutrally e. under purifying selection; under positive selection 3. You might have an MHC allele that shares a more recent common ancestor with the MHC allele of a chimp than with your roommate’s allele at that same locus. This is because MHC alleles have experienced _______________________, which tends to ____________________ coalescence times. a. Balancing selection; increase b. Balancing selection; decrease c. Directional selection; not affect d. Directional selection; increase e. Neutral evolution; increase 4. Referring to the tree to the right, which is an accurate statement about relationships? a. gorilla is more closely related to an orangutan than a human b. a gorilla is equally related to a human and an orangutan c. an orangutan is equally related to gorillas and gibbons d. a tarsier is more closely related to a human than it is to a lemur e. lemurs are the ancestors of primates 2
5. The codon TTA codes for leucine. If a new mutation occurred that replaced the “A” with a “G,” this mutation would be _______________ and its fate would most likely be determined by ___________. a. nonsynonymous; genetic drift b. nonsynonymous; natural selection c. synonymous; genetic drift d. synonymous; natural selection e. synonymous; purifying selection 6. Which of the following statements accurately describes Hox genes: a. they code for traits such as legs or wings in the developing embryo b. their expression gives positional information to other genes c. they are transcription factors d. a and b are correct e. b and c are correct 7. The tree to the right shows the number of replacement and synonymous substitutions in the gene FOXP2 for several lineages of primates. These data support the hypothesis that FOXP2 has experienced __________________ in the lineage leading to mice. a. stabilizing selection b. purifying selection c. drift d. positive selection e. alien intervention 8. If species A and B are more closely related to each other than either is to species C, then species A and B must : a. share a more recent common ancestor b. be more similar physically overall c. share more derived homologies (synapomorphies) d. both a and c are correct e. a, b, and c are all correct 3
9. Dobzhansky-Mueller incompatibilities are a mechanism for the evolution of _______________________ through negative___________________ between alleles originally favored in allopatric populations. a. postzygotic isolation; epistasis b. premating isolation; epistasis c. prezygotic isolation; pleiotropy d. prezygotic isolation; epistasis e. postzygotic isolation; pleiotropy 10. Two genes that are paralogs: a. arose from gene duplication b. are found in the same genome c. may perform the same or different functions d. all of the above e. none of the above 11. Given the tree above which of the following statements is correct? a. An alligator is more closely related to a bird than it is to a lizard b. The dog evolved before the turtle c. A frog is the most recent ancestor of a dog d. All of the above e. None of the above 12. Drosophila mojavensis and Drosophila arizonae are closely related, and reproductive isolation between them is incomplete. They have overlapping distributions in the Sonoran desert, although there are also areas where they occur allopatrically. Which of the following conditions would be required in order to infer reinforcement? a. premating isolation is stronger in areas where they are allopatric than in areas where they are sympatric b. hybrids have lower fitness c. premating isolation is stronger in areas where they are sympatric than in areas where they are allopatric d. b and c are both required e. a and b are both required 4
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