The Hardy-Weinberg principle states that a population’s allele and genotype frequencies will remain constant throughout generations; it assumes that in a given population, the population is large and is not experiencing mutation, migration, natural selection, or sexual selection.
Hardy-Weinberg equilibrium is achieved when the gene frequencies in a population do not change over time. This means the population is not evolving. There are five conditions for Hardy-Weinberg equilibrium.
1. no mutations
2. no immigration/emigration
3. no natural selection
4. no sexual selection
5. a large population
The Hardy-Weinberg principle can be used to estimate the frequency of alleles and genotypes in a population. The frequency of alleles can be estimated by calculating the frequency of the recessive genotype, then calculating the square root of that frequency to determine the frequency of the recessive allele. The frequency of alleles in a population can be represented by:
p + q = 1
where p= the frequency of the dominant allele; and q= the frequency of the recessive allele
The frequency of genotypes in a population can be represented by:
p2+2pq+q2= 1
where p2= the frequency of the homozygous dominant genotype; 2pq= the frequency of the heterozygous genotype; and q2= the frequency of the recessive genotype
Practice Questions
Khan Academy
MCAT Official Prep (AAMC)
Online Flashcards Biology Question 13
Key Points
• The Hardy-Weinberg principle assumes that in a given population, the population is large and is not experiencing mutation, migration, natural selection, or sexual selection.
• The frequency of alleles can be estimated by calculating the frequency of the recessive genotype, then calculating the square root of that frequency to determine the frequency of the recessive allele.
• The frequency of alleles in a population can be represented by p + q = 1, with p equal to the frequency of the dominant allele and q equal to the frequency of the recessive allele.
• The frequency of genotypes in a population can be represented by p2+2pq+q2= 1, with p2 equal to the frequency of the homozygous dominant genotype, 2pq equal to the frequency of the heterozygous genotype, and q2 equal to the frequency of the recessive genotype.
Practice Questions
https://jackwestin.com/khan-academy-mcat/a-family-history-of-marfan-syndrome
Key Terms
genotype: the combination of alleles, situated on corresponding chromosomes, that determines a specific trait of an individual, such as “Aa” or “aa”
phenotype: the appearance of an organism based on a multifactorial combination of genetic traits and environmental factors, especially used in pedigrees
allele: a variant form of a gene
mutation: a permanent alteration in the DNA sequence that makes up a gene
natural selection: the survival and reproduction of individuals due to differences in phenotype
Hardy–Weinberg equilibrium: states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences
gene frequency: the proportion of a population that carries one type of allele
recessive: able to be covered up by a dominant trait
dominant: a relationship between alleles of a gene, in which one allele masks the expression (phenotype) of another allele at the same locus
homozygous: of an organism in which both copies of a given gene have the same allele
heterozygous: of an organism which has two different alleles of a given gene