Population Genetics Flashcards
Hardy Weinberg Equilibrium (what is it and what equations are used?)
-Connection between allele frequency and genotype frequency in population
Allele Freq: p + q=1
Genotype Freq: p^2 + 2pq + q^2 = 1
How to decide if a population is in HWE?
1- Calc OBSERVED genotype frequency (based on phenotype data)
2- Convert to OBSERVED allele frequency
3- Calc predicted genotype freq if in HWE (using observed allele frequencies)
**If observed and predicted genotypes are the same then population is in HWE
5 Factors That Disrupt HWE
1- Non-random mating (inbreeding or assortative mating)
2- Small population size (genetic drift, founder effect)
3- Migration
4- Mutation
5- Selection
**All must be happening in CURRENT generation
Why is Inbreeding so Bad?
-Increases homozygosity in all loci across genome
Assortative Mating
Preferential mating w/ same phenotype (height, deafness, intelligence, socioeconomic status)
-Less dangerous than inbreeding because only genes involved in these preferences are not in HWE
Genetic Drift
-If population is really small then allele frequency will change from one generation to the next simply due to CHANCE
Founder Effect
New population will have diff gene frequencies than parent population (where founders came from)
Mutation-Selection Balance
- Mutation = introduce new disease-causing variation
- Selection = removes disease causing variation b/c person w/ disease does not reproduce
- Dom diseases almost always caused by new mutation b/c mutation introduced and selected against all b/f mutation can be passed to next generation
- Rec alleles more common b/c carriers are not selected against
Heterozygote Advantage
-When disease-causing allele is more common than you would predict –> selection favors heterozygotes over both homosygotes (hetero must provide some sort of protective function)
ex- sickle cell carriers and malaria
