1.
What is a quantitative trait, and how do quantitative traits differ from qualitative traits? Describe East's investigation into whether or not quantitative traits are inherited according to basic Mendelian principles. What two key predictions did he make? Were they met?
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2.
Describe the general process of QTL mapping, with special attention to the associations investigators look for between genotypes at marker loci and phenotypes and using Bradshaw et al.'s study of monkey flowers to illustrate. How did they verify that the QTL's they identified were, in fact, the loci subject to natural selection during the diversification of the two species they investigated? In general, what can QTL mapping tell us about quantitative trait loci. What can it not tell us?
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3.
Describe the two different views, exemplified by Ronald Fischer and H. Allen Orr, about the phenotypic effects of the alleles fixed by natural selection (and that are responsible for adaptive differences between species). Whose view did Bradshaw et al's work on monkeyflowers support? Defend your answer using information from Figure 8.8 on page 298 of your textbook.
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4.
Using Benjamin et al.'s study of novelty seeking and Ogura et al.'s study of Crohn's disease to illustrate, describe how investigators can identify QTL and the proteins they encode. In general, what associations are required? How were these associations demonstrated in the two sample studies?
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5.
Define "heritability," clearly explaining what this quantity does and does not measure. Define the broad-sense heritability, clearly explaining the relationship among heritability, phenotypic variation, genetic variation, and environmental variation.
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6.
Describe how narrow-sense heritability is measured using plots of midparent and midoffspring trait values. Under what condition(s) is this method valid? Use Smith and Dhondt's study of heritability in beak size in song sparrows to illustrate. Describe the logic of using twin studies to measure heritability using McClearn et al.'s study of cognitive ability in a Swedish population to illustrate.
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7.
Explain the conceptual relationship between measuring differences in fitness and measuring the strength of selection. Describe how to calculate the selection differential and the selection gradient using DiMasso et al.'s studies of tail length in laboratory mice to illustrate. Is one of these two measures preferred over the other? Why or why not? Justify your answer using the Grant's study of beak size in Galapagos finches as an example (and be sure to address the important findings of that work).
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8.
Describe the conceptual basis of the response to selection (R). In biological (rather than mathematical) terms, explain its relationship to heritability and selection differential.
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9.
Describe Galen's experimental studies of selection on flower size in alpine skypilots. Be sure to clearly identify the questions she asked, the hypotheses she tested and the ways in which her experiments allowed her to use the techniques of quantitative genetics. What were her findings and conclusions?
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10.
Define the term "mode of selection." For each major mode of selection, describe the "direction" of selection, the relationship between fitness and values of the trait in question, and how the mean value and variance of the trait will change over time (this information is presented graphically below). Give at least one good example of each (be sure you include the experimental or observational evidence in support of your examples).
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11.
What is the "evolutionary puzzle" presented by the assumption that directional and stabilizing selection are the most common modes of selection? What are some possible solutions to the puzzle? Describe how Elena and Lenski tested these possibilities using E. coli bacteria.
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12.
Discuss the key flaws in Murray and Herrnstein's claim (in The Bell Curve) that differences in IQ between African Americans and European Americans is due to genetic differences between the two groups. Be sure to address the utility (or lack thereof) of using heritability to understand differences among populations. Ideally, what kind(s) of experiments could we do to test Murray and Herrnstein's claim directly? What kinds of outcomes might such experiments produce, based on work with other organisms?
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