Hardy-Weinberg Principle
Describes the conditions under which allele and genotype frequencies in a population remain constant from generation to generation in the absence of evolutionary influences.
What is Hardy-Weinberg Principle?
The relative frequency of a particular allele in a population, expressed as a proportion or percentage.
Key formula / rule: Allele Frequency Equation
Key points
- Understand the conditions required for Hardy-Weinberg equilibrium.
- Explain the significance of the principle in evolutionary biology.
- Calculate allele and genotype frequencies using the Hardy-Weinberg equations.
- Identify evolutionary forces that disrupt equilibrium.
Common exam trap
Assuming that Hardy-Weinberg equilibrium is a description of how evolution actually happens, rather than a baseline for detecting it.
Definitions
- Term
Allele Frequency
- Meaning
The relative frequency of a particular allele in a population, expressed as a proportion or percentage.
- Term
Genotype Frequency
- Meaning
The relative frequency of a particular genotype in a population, expressed as a proportion or percentage.
- Term
Population Genetics
- Meaning
The study of the distribution and change in frequency of alleles within populations, and of the consequences of these changes.
- Term
Evolutionary Equilibrium
- Meaning
A state where allele and genotype frequencies in a population remain unchanged from generation to generation.
Learning objectives
Understand the conditions required for Hardy-Weinberg equilibrium.
Explain the significance of the principle in evolutionary biology.
Calculate allele and genotype frequencies using the Hardy-Weinberg equations.
Identify evolutionary forces that disrupt equilibrium.
Formulae
- Name
Allele Frequency Equation
- Note
p represents the frequency of the dominant allele, and q represents the frequency of the recessive allele.
- Expression
p + q = 1
- Name
Genotype Frequency Equation
- Note
p² is the frequency of the homozygous dominant genotype, 2pq is the frequency of the heterozygous genotype, and q² is the frequency of the homozygous recessive genotype.
- Expression
p² + 2pq + q² = 1
Prerequisites
Basic Mendelian genetics (alleles, genotypes, phenotypes)
Understanding of population genetics
Basic probability concepts
Common mistakes
Assuming that Hardy-Weinberg equilibrium is a description of how evolution actually happens, rather than a baseline for detecting it.
Incorrectly applying the equations to populations that are clearly not in equilibrium.
Forgetting to check all five conditions before concluding equilibrium.
Confusing allele frequencies (p, q) with genotype frequencies (p², 2pq, q²).
Keywords
Hardy-Weinberg Principle
Population Genetics
Allele Frequency
Genotype Frequency
Genetic Equilibrium
Evolutionary Forces
Null Hypothesis
p + q = 1
p² + 2pq + q² = 1
Practice preview
If a population is in Hardy-Weinberg equilibrium, which of the following statements is true regarding allele frequencies?…
easy
In a population, the frequency of the homozygous recessive genotype (aa) is 0.09. Assuming the population is in Hardy-Weinberg equilibrium, what is the frequency of the heterozygous genotype (Aa)?…
medium
The Hardy-Weinberg principle states that allele and genotype frequencies in a population will remain constant from generation to generation if certain conditions are met. Which of the following is NOT a condition for Har…
easy