Lecture 13 & 14: Linkage & Quantitative Genetics Flashcards
Define haplotype
a set of DNA variations, or polymorphisms, that tend to be inherited together.
Know how to calculate allele frequencies.
(# of a specific allele)/(total # of chromosomes)
What is the relationship between chromosome frequencies and the product of 2-locus allele frequencies in LD and LE?
chromosome frequencies = product of 2-locus allele frequencies in LE, and do not equal one another in LD.
What forces can change a population to have LD?
- Selection
- Mutation
- introduction of a mutation and subsequent selection
- Drift
- can cause LD in a finite population
- Population mixture
What is the relationship with LD and distance and time?
LD decays with distance (one allele from the other) and time (# of generations). The greater the distance the greater the rate of recombination.
What is the maximum D value and how is it calculated?
f(AB) = f(ab) = 0.5, so D = 0.5 x 0.5 – 0.0 x 0.0 = 0.25
Maximum D values = 0.25
Define EHH
EHH = extended haplotype homozygosity, the higher the frequency and the farther the association extends from the locus on interest, the stronger the recent selection must have been.
Define quantitative genetics
genetic basis of continuous variation
Understand the additive model
alleles from any locus are “Added together” to determine phenotype
Understand Pascal’s triangle and binomial expansion
As more genes are added (each with 2 allele) the number of recombination increases
What is phenotypic variation composed of?
Phenotypic variation = genotypic variation + environmental variation
What is genetic variation composed of?
Additive + dominance + interaction variation
Define epistasis
the interaction of genes that are not alleles, in particular the suppression of the effect of one such gene by another.
when the effect of one gene depends on the presence of one or more modifier genes’ (genetic background).
Define heritability
Proportion of phenotypic variation due to genetic variation, = VG/VP = slope of parent offspring regression
What is Pbar and P*?
Pbar = mean of parens before selection, P* mean of selected parents, P*-Pb = selection differential, S
