Unit 7: Topic 5 - Hardy-Weinberg Equilibrium

Question 1

What is the Hardy-Weinberg model for and what conditions need to be met for Hardy-Weinberg Equilibrium?

Answer 1

The model is for predicting future allele frequencies in a population that is in Hardy-Weinberg equilibrium. This equilibrium is met when a population satisfies these conditions: a large population size, random mating, no migration/gene flow, no mutations, and no natural selection.

Question 2

What is the Hardy-Weinberg equation and what does each variable represent?

Answer 2

The Hardy-Weinberg equation is: p² + 2pq + q² = 1 with p + q = 1 and it is meant to calculate the allele frequencies from genotype frequencies. The variable p represents the dominant allele frequency in the population while the variable q represents the recessive allele frequency. p² represents the homozygous dominant frequency, while the q² represents the homozygous recessive frequency, and the 2pq represents the dominant heterozygous frequency. The =1 part of the equation represents the total percentage the frequencies add up to, which is 1 or 100%.
Mathematically, an allele can be found by square rooting q² or p², depending on the problem, or subtracting the known allele from 1 to get the unknown allele (p + q = 1). In select problems, divide the number of individuals by the total number of individuals to get a phenotypic frequency.

Question 3

How do changes in allele frequencies contribute to the theory of evolution?

Answer 3

The changing of allele frequencies supports the concept of natural selection due to the necessity of an allele becoming more dominant than others through the selection for it. The allele that would be dominant would be the most advantageous phenotype for the organism and would increase it and its offspring’s fitness. This violates the Hardy-Weinberg equilibrium and supports the idea of an evolving population.

Question 4

What impacts would occur on a population that did not satisfy the condition of a large population size in Hardy-Weinberg’s equilibrium?

Answer 4

A small population would be impacted greater by abiotic and biotic factors due to its small gene pool size and, in turn, lower adaptability. If an environmental change were to occur, such as a natural disaster or weather change, the small population could go extinct. Or in another case, a small population of bacteria would have a much smaller chance of survival if an antibiotic were introduced than a large population of bacteria with a larger gene pool.