Genetic Diversity and the Hardy-Weinberg Principle

Genetic Diversity in Populations

• A population is a group of organisms of the same species living in the same area
• Within a population are many genes
• The gene pool includes all genes and their alleles
• Population geneticists study the gene pool to assess population health and microevolutionary changes

The Hardy-Weinberg Principle

• A mathematical method to study the gene pool
• Predicts a population's gene pool remains stable if other factors are constant
• Any changes in gene frequencies over time can be observed
• For equilibrium (no evolution):
  • No mutations introducing new alleles
  • No gene flow (migration)
  • Random mating
• The population must be large (to prevent genetic drift) and no natural selection occurs

Genotype, Phenotype, and Allele Frequency

• Genotype frequency: count of organisms with a specific genotype
• Phenotype frequency: count of organisms with a specific phenotype
• Allele frequency: proportion of a particular allele in the entire population

The Hardy-Weinberg Equations

• p² + 2pq + q² = 1
  • p and q are allele frequencies
  • p² = homozygous dominant frequency
  • q² = homozygous recessive frequency
  • 2pq = heterozygous frequency
• p + q = 1

Sample Calculations

• Example calculations are from text pages 722, 8a, and 8b

Examples

• Example involving a population of pigs, where 80% display the dominant pink coat color trait and 20% have the recessive black coat color.
• Calculation of allele and genotypic frequencies is required

Other Types of Problems

• Snail example
• Another example of problems

Evolutionary Change

• Gene pools can be unstable
• Mutation
  • Randomly occurring events in gametes
  • Creates genetic diversity
  • Can be neutral, beneficial, or harmful
• Lack of diversity risks extinction
• Gene flow
  • Alleles exchanged between populations due to migration
  • Increases genetic variability
• Natural selection
  • Mutations provide raw material
  • Example of sickle cell anemia
  • Heterozygote advantage
• Non-random mating
  • Mates chosen based on traits or behaviours
    • May lead to sexual dimorphism
• Genetic drift
  • Occurs in all populations, especially small ones
  • Change in gene pool due to chance
  • Founder effect (isolated population with a subset of original gene pool)
• Bottleneck effect
  • A sudden decrease in population size reduces gene pool diversity

This quiz covers the concepts of genetic diversity within populations, focusing on the gene pool and the role of population geneticists. It also explores the Hardy-Weinberg Principle, a mathematical approach to studying gene stability and the conditions necessary for a population to remain in equilibrium. Test your understanding of genotype, phenotype, and allele frequencies as you delve into population genetics.