Figure 9.12 (continued)

Interact box 9.3 Response to selection and the number of loci that cause quantitative trait variation

Use the QTL module in PopGene.S2 to simulate response to selection for a quantitative trait that has genotypic variation caused by either few loci or by many loci. The key parameter to vary is the number of loci that underlie the quantitative trait, nQTL. Select the option for All loci have equal effects and try nQTL = 10 and nQTL = 100. Set the other simulation parameters at Natural selection phenotypic value truncation point = 0.5 (only individuals in the upper 50% of phenotypic value reproduce), N = 250, mutation rate = 0.0, generations = 100, VE = 0.1, Maximum genotypic value = 10.0.

What is the heritability over time with nQTL = 10 or nQTL = 100? How does an increase in environmental variation (VE = 0.1 or, say, VE = 1.0) influence your conclusion?

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