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What are the assumptions of the HWE?

- mutations can be ignored
- migration is negligible (no gene flow)
- mating is random
- no selective pressure
- large population size
- equal allele frequencies in each sex


What is the underlying principle of the HWE?

p + q = 1,

where p = dominant allele frequency
and q = recessive allele frequency


What is gene flow and give an example?

- new alleles give rise to increased mutations
- new alleles introduced my migration/intermarriage
- new gene frequency

e.g. Vikings populating Ireland/Scotland


Name two types of non-random mating?

Assortative mating; partners with shared characteristics

Consanguinity; mating between close blood relatives


What happens as a result of negative natural selection?

- decreased fitness
- decreased trait prevalence
- decreased alleles


What happens as a result of positive natural selection?

- increased fitness
- increased trait prevalence
- increased heterozygote advantage


What is heterozygote advantage?

carrying the gene for a certain recessive condition can give rise to resistance on another condition

e.g. sickle cell anaemia = malaria resistance in tropical Africa
cystic fibrosis = cholera/typhoid resistance in western Europe


What is genetic drift?

statistical drift of gene frequencies due to random events (beetles by the pond)


What is the founder effect?

reduced variation when a small subset of a large population is used to start a new colony
(the bottleneck effect)