Population Genetics

What is the Hardy–Weinberg equation?

p² + 2pq + q² = 1

What does p² represent?

Frequency of homozygous dominant (AA)

What does 2pq represent?

Frequency of heterozygotes (Aa)

What does q² represent?

Frequency of homozygous recessive (aa)

***How do you estimate carrier frequency from disease prevalence?***

Use q² = prevalence → q = √prevalence → 2pq ≈ 2q (if p ≈ 1)

What is a haplotype block?

A segment of DNA with tightly linked variants inherited together

How do haplotype blocks arise?

From recombination events over generations

What is linkage disequilibrium?

Non-random association of alleles at nearby loci

How are haplotype blocks used in mapping?

Tag SNPs identify blocks associated with disease traits

What is the smallest unit of linkage disequilibrium?

Haplotype block

Why do recombination events reduce haplotype size over time?

They break up ancestral blocks into smaller segments

Genetic drift

random changes in an allele

Gene flow

change in frequency of allele ex: migration leads to introduction of new genes

Genetic bottleneck

sharp population reduction (ex: persecution of a particular group), leads to decrease in allele diversity

Founder effect

population expansion from a small size (ex: genghis khan)