Quantitative Genetics

Question 1

What’s the difference between continuous and discrete variation?

Answer 1

Discrete- limited

Continuous- unlimited

Question 2

What are some of the mechanisms behind the existence of continuous variation in populations?

Answer 2

Environmental and genetic factors working together, or multiple genes working together

Question 3

Without getting into the math, what do we generally mean by “variance?”

Answer 3

Variation within the population

Question 4

How can phenotypic variance be broken down into different components? Why is this important for understanding the effect of natural selection?

Answer 4

It can be broken down into genetic and environmental components, which is important for demonstrating interplay between two factors involved in natural selection

Question 5

What does heritability represent in terms of phenotypic variance?

Answer 5

Relationship between parents and offspring phenotypes (0 indicating no relationship, 1 identical)

Question 6

What’s the difference between broad-sense and narrow-sense heritability?

Answer 6

Broad-sense- encompasses all of the genetic input to the trait
Narrow-sense- proportion of phenotypic variation that is passed between parent and offspring in a straight forward, predictable way

Question 7

How is heritability measured in populations? What are some of the pitfalls associated with measuring heredity?

Answer 7

Midparent regressions- slope of a linear regression between average mother/father phenotype and average offspring phenotype

Question 8

How does the breeder’s equation work? What are the parameters that go into it? What do they mean?

Answer 8

R- response to selection in the offspring generation
S- selection differential in the parental generation
h^2- slope of the midparent regression x2

Question 9

What are some limitations of making strong inferences about calculated heritability in complex populations like humans?

Answer 9

Transgenerational epigenetics and maternal effects (ie pre-pubescent nutrition and its effect on diabetes, obesity, and mortality)

Question 10

When I said that quantitative genetic parameters are only meaningful for a given population in a given environment, what did I mean?

Answer 10

Genetics, environment, etc are differ across populations and therefore parameters are different

Question 11

Why are differences in heritable traits among populations not necessarily driven by genetic differences among those populations?

Answer 11

Additional parameters, such as environment, also play a role