Hardy-Weinberg Equilibrium
The Hardy-Weinberg equilibrium is foundational in understanding how populations evolve genetically over time. Proposed in 1908, it predicts that the genetic variation in a population will remain constant in the absence of evolutionary forces. Therefore, for a population to be in Hardy-Weinberg equilibrium, it must fulfill the following requirements:
An extremely large population size
Random mating
No mutations
No gene flow (no alleles entering or exiting the population)
No natural selection
When these conditions are met, the following mathematical equation can be used to predict the frequencies of genotypes.
The variables p and q represent the frequencies of two alleles, and the equation can be used to predict the frequencies of genotypes (homozygous dominant (pp), heterozygous (pq), and homozygous recessive (qq). It should be noted that the values for p and q will always add up to 1.
Problem:
In a population of 1,000 individuals, the allele for black fur (B) is dominant over the allele for brown fur (b). The frequency of the black fur allele (B) is 0.6. Calculate the expected genotype frequencies under Hardy-Weinberg equilibrium.
Solution:
To solve a Hardy-Weinberg equilibrium problem, start by determining the frequency of one allele in the population (B is 0.6), as well as the total population size (1,000). Subtract this frequency from one to find the frequency of the other allele (b=0.4). Next, calculate the proportion of individuals expected to have each genotype: those with two dominant alleles (0.36), those with one dominant and one recessive allele (0.48), and those with two recessive alleles (0.16). These proportions are obtained by squaring the frequency of each allele for the homozygous genotypes and multiplying twice the product of the two allele frequencies for the heterozygous genotype. Finally, multiply these proportions by the total population size to determine the number of individuals with each genotype (360, 480, and 160).
Author: Sanjay Adireddi
References: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7083100/
