# L17 Quantitative Genetics 2 Flashcards

For complex quantitative traits

- degree of resemblance within families is a function of the genetic basis of the trait
- but the phenotypic value of the offspring is NOT exactly equal to the mean value of the parents
- the resemblance between relatives can be formally calculated under the additive quantitative genetics model

Level of relatedness

level of relatedness between individuals is expected to lead to some trait similarity

Genetic covariance

trait similarity between relatives is formally calculated in terms of genetic covariance

Heritability

proportion of genetic variance compared to the total variance is called heritability

- makes strong assumptions: linear decomposition of effects (G and E) and no covariation/interaction among them
- strictly population specific, which means that any change in allele freq change its value

Response to selection

knowing the level of heritability allows us to predict the response to selection of a population across generations

Variance

variance of a variable is a measure of the deviation of the observed values from the expected mean

- genetic values being fixed, genetic variance is due to randomness of allele frequency

Covariance

covariance of two variables is a measure of the joint variability of two variables e.g. how the two variables deviate jointly from their expected mean

- in genetics, the covariance between individuals for a trait is directly proportional to their level of relatedness

Degree of identity

IBD - estimated from pedigree of individual

IBS - determined from sequence data

Covariance between parent and offspring

See onenote

Covariance between genetic effects

see onenote

Covariance between sibs

see onenote

covariance between any relatives

see onenote

Partitioning the phenotype variance among and within families

see onenote

ANOVA

covariance between individuals of a family is by definition the variance among families

Broad-sense heritability

ratio of genetic variance and the total phenotypic variance e.g. metric of how much trait variation is due to genetics

Narrow-sense heritability

how much of the phenotype variance can be immediately transferred to the next generation