In this lecture, we pivot from describing behavioral methods for disentangling nature (genetics) from environment (nurture) and turn toward more quantitative approaches to assessing heritability and the contribution of genes to phenotype. First, we return to the topic of "heritability" as a measure of the contribution of genetic variance to observed phenotypic variance and define two different forms of heritability – broad-sense heritability (which includes non-additive genetic effects) and narrow-sense heritability (which only includes additive genetic effects). We show how to use parent–offspring phenotypic analyses to measure narrow-sense heritability ("h squared"). As heritability will vary in a population if the corresponding trait is under selection, we then discuss how to use genetic analyses to infer whether a population is at equilibrium or currently in the process of evolving through selection or by other means. This gives us an opportunity to discuss the "Hardy–Weinberg equilibrium" and discuss some practical ways to use it. We then conclude with an introduction to QTL mapping and GWAS for understanding which combinations of genes contribute to a particular behavior (and how).
Topic highlights:
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- heritability: broad-sense and narrow-sense
- effect of selection on heritability
- Hardy–Weinberg equilibrium/principle
- quantitative trait loci (QTLs) and QTL mapping
- genome-wide association studies (GWAS, GWA studies)
Important terms: heritability, narrow-sense heritability, broad-sense heritability, Hardy–Weinberg equilibrium, quantitative traits, quantitative trait loci (QTL), QTL mapping, genetic markers, single-nucleotide polymorphisms (SNPs), linkage map, genome-wide association study (GWAS, GWA study)
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