Chapter 18

Explain why some complex traits are also called quantitative traits, and give at least one example.

Name several factors that influence variation in complex traits.

Explain why it does not make sense to try to separate the effects of genes ("nature") and the environment ("nurture") in a single individual, while it does make sense to separate genetic and environmental effects on differences among individuals.

Explain how you would go about determining the relative importance of genes and the environment for variation in risk for a complex trait such as type 2 diabetes.

Graph a trait, like human height, with height on the \(x\) -axis and number of individuals on the \(y\) -axis, and describe the shape of the resulting graph.

Explain why the effect of a genotype on a phenotype cannot always be determined without knowing what the environment is, and why the effect of a particular environment on a phenotype cannot always be determined without knowing what the genotype is.

Define "regression toward the mean" and explain why it occurs for complex traits.

Define the heritability of a trait and explain why the heritability of a given trait depends on the population being studied.

Define twin concordance and explain how twin studies can be used to investigate the importance of genetic and environmental factors in the expression of a trait.

For a typical complex trait, describe the relationship between the number of genes affecting the trait and the magnitude of their effects on the trait.

Explain what personalized medicine is and how it relates to complex traits such as human diseases.