Lecture Twenty One : Population genetics and natural selection
4 important questions on Lecture Twenty One : Population genetics and natural selection
How do you calculate the genotype frequencies using Hardy-Weinberg equilibrium ?
We can look at alleles separately:
- Two alleles in a population, a dominant and a recessive, then there frequencies add up to one.
- p+q=1
Or within their inherited genotypes:
- p 2+2pq +q2=1
- p2=homozygous dominant
- pq= heterozygous
- q2=homozygous recessive
What are the random genetic drift the occurs rapidly in small populations ?
Changes can occur via:
- Non-random mating
- Natural Selection
- Gene Flow or Migration
- Mutations
- Random Genetic Drift
- Bottleneck
- Founder Effect
What is Random Genetic Drift ?
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How do populations evolve over time in response to selection ?
- Directional : Selection pressure against short necks of giraffes
- Stabilising : Selection against short plants because they aren’t getting sun. Tall plants get wind damage.
- Disruptive : light and dark coloured oysters
- Frequency Dependent Selection : This is where it is favoured to have an uncommon allele
- Cline : This is where gradual geograhical change causes a gradual change in genetic/phenotypic composition
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