Population genetics and human disease Flashcards
What defines a population in population genetics?
A group of individuals of a single species living together, capable of interbreeding (if sexual).
What is the gene pool of a population?
The collection of all alleles present in the population.
How is allele frequency calculated?
Frequency of allele (p/q): Proportion of that allele among all alleles in the population.
Example: If 70% of alleles are blue,
𝑝
=
0.7
p=0.7.
What are the assumptions of Hardy–Weinberg equilibrium?
Random mating.
No mutations.
No migration.
Very large population size.
No natural selection.
What happens when HWE assumptions are violated?
Non-random mating affects genotype frequencies but not allele frequencies.
Mutation introduces new alleles.
Migration changes allele frequencies.
Small populations cause genetic drift.
Selection favors specific alleles or genotypes.
What are the main forces that change allele frequencies?
Mutation: Creates new alleles.
Migration: Introduces alleles from other populations.
Genetic Drift: Random fluctuations in small populations.
Selection: Favors specific alleles or genotypes.
Assortative Mating: Positive increases homozygosity; negative increases heterozygosity.
What is genetic drift?
Random changes in allele frequencies, more significant in small populations.
Example: Bottleneck effect reduces genetic diversity.
What is the outcome of genetic drift simulations?
Alleles can drift to fixation (100%) or elimination (0%).
How does selection affect allele frequencies?
Differential reproduction favors certain alleles.
Directional Selection: One allele becomes fixed.
Balancing Selection: Heterozygotes have an advantage (e.g., sickle-cell allele against malaria).
What is frequency-dependent selection?
Allele advantage changes based on its frequency in the population.
What is a haplotype?
A group of alleles inherited together from a single parent.
How does a mutation affect HWE?
Introduces a new allele, altering allele frequencies.
