Population Genetics (Lec. 22)

Lecture 22

Population Genetic

How allele frequences change in a population due to evolutionary forces

• Change in genetic make-up over time

• Explains how evolution happens by tracking how common different genes become.

Puente Square

Predict outcome of genetic cross

• Genotype Ratio: Tells genotype of the 4 individuals

• Phenotypic Ratio: Dom will overpower recessive allele

Gene Frequency

How common each allele is in a population

• Proportion of all alleles at a gene that are a specific type

• Ability to see how individuals will express genes, helps know individuals that belong in population or not.

Allele Frequency

How common each allele is in a population

• Percentage/proportion of all copies of a gene that are a certain allele

• Proportion of different alleles within a population.

p and q (allele frequency)

Represent allele frequency of any given allele pair: p + q = 1

• p = frequency for the dominant allele

• q = frequency of recessive allele

Frequencies (allele)

1 = Fixed allele, no variants

0 = allele absent from population

0.5 = half of all alleles in population

Hardy-Weinberg Equilibrium

Allele & genotype frequencies stay the same from generation to generation if nothing is acting on the population.

• Gives population time to grow/breed to reach equilibrium.

• If nothing changes the populations & the genetics stay the same

• Formula: p² + 2pq + q² = 1

Genetic Drift

Random changes in allele frequencies, strongest in small populations

• Allele frequencies change by chance, not because they are better or worse.

• When alleles in population increase or decrease overtime