Lecture 8 Microevolution Flashcards
State when to use the Hardy Weinberg equation to calculate genotype/allele frequencies
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State the 5 Assumptions of the Hardy-Weinberg Equilibrium.
- Large population size
- Random mating
- Mutations
- ## no migration or gene flow
State the 5 mechanisms that alter allele frequencies in a population
- Non random mating
- Migration / Gene flow
- Mutations
- Natural selection
- Genetic drift
State the mechanisms in place to preserve genetic variation in a population
- Diploid factors
- Balancing selection
- Neutral alleles (synonomous point mutations)
- Clinial variation
Define Balancing selection
Also known as heterozygote advantage. an example of this is sickle cell anaemia, where the heterozygote has higher fitness than the homozygotes.
Explain what is meant by diploid factors of organisms
This refers to a situation where a deleterious allele is hidden by the heterozygotes hence avoiding being selected against.
How does a population preserve the alleles in a population
- Natural selection selects against the recessive homozygous phenotypes (thus favours heterozygotes)
- Deleterious alleles are preserved in the heterozygous phenotypes.
- CF is a recessive gene disease.
What does a deviation from the Hardy Weinberg equilibrium reveal
That the alleles/genotypes are no longer at equilibrium and thus suggest that something interesting is happening to cause a change in allele/genotype frequency.
State two extreme examples of genetic drift
- Founder and bottleneck effects
Gene flow
Migration of individuals or transfer of gametes across populations hence transferring alleles
Define genetic drift
These are random chance fluctuations in allele frequency.
Explain what is meant by the bottleneck effect
This occurs when a natural event drastically reduces the population size. Eg a natural disaster, where most of the population is killed, and only a small amount of individuals remain, small gene pool remains.
Explain what is meant by the Founders’ effect
This would occur if me anD went to Mars and repopulated. As the
Define gene flow
The migration of individuals or transfer of gametes across populations hence transferring alleles.
Define and explain what is meant by neutral alleles
Allelic variants that do not alter the fitness of the organism. These are synonomous point mutations that do not alter the protein product. Silent mutations.
