Hardy–Weinberg Principle Explains Genetic Stability in Populations
Definition
The Hardy–Weinberg principle
The Hardy–Weinberg principle is a mathematical model that predicts how allele and genotype frequencies remain constant in a population—unless evolutionary forces act upon it.
- This principle is foundational for understanding genetic stability and changes in populations.
Using the Hardy–Weinberg Equation
- The equation is expressed as:
$$p^2 + 2pq + q^2 = 1$$
- Where:
- $p$ = frequency of the dominant allele.
- $q$ = frequency of the recessive allele.
- $p^2$ = frequency of homozygous dominant individuals.
- $q^2$ = frequency of homozygous recessive individuals.
- $2pq$ = frequency of heterozygous individuals.
When using the Hardy–Weinberg equation, always start by calculating $q^2$ if you know the frequency of a recessive phenotype. This makes it easier to find $q$ and $p$.
How to Calculate Allele Frequencies
- Identify the frequency of homozygous recessive individuals ($q^2$).
- Take the square root of $q^2$ to find $q$ (recessive allele frequency).
- Use $p + q = 1$ to calculate $p$ (dominant allele frequency).
