Hardy Weinberg Law

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Hardy Weinberg Law Notes

In the lack of any evolutionary influences onto another generation, the genotype and allele frequencies stay constant in a large, random-mating population. Influences include mate preference, genetic drift, mutation, gene flow, sexual choice, founder effect, genetic hitchhiking, meiotic drive, population bottleneck, inbreeding and assortative mating.

Genotype frequencies and allele frequencies are linked to one another in a way that certain allele frequencies are squarely extended. In other words, the Hardy Weinberg law states that the predicted frequency of genotypes can be calculated in a population below a certain restricted number of assumptions, given that the frequency of various alleles in a population has already been understood.

Consider a single locus carrying only two alleles represented by A and a with corresponding frequencies f(R) = p and f(r) = q respectively, then the genotype frequencies that can be assumed to be spontaneous mating under restricted conditions are

f(RR)= p2 for AA homozygotes

f(rr) = q2 for aa homozygotes

f(Rr) = 2pq for heterozygotes

The hardy weinberg equation is represented by the following equation:

p2 + q2 + 2pq = 1

In the exclusion of some kinds of factors including evolution, natural selection, genetic drift, etc. between one generation to another, the allele frequencies p and q tend to remain constant. This is how you can achieve equilibrium.

What is the Hardy Weinberg Principle?

The statute is named after G.H. Hardy and Wilhelm Weinberg. They were leaders in mathematically demonstrating this idea, also known as the Hardy-Weinberg equilibrium, law, model or theorem.

Hardy Weinberg principle is a theory which states that in the absence of disrupting factors, genetic diversity in a population would stay constant from one period to the next. In a large population with no destructive conditions, when mating is random, the law assumes that both genotype and allele frequencies will stay constant since they are in balance.

Hardy's work focused on debunking the view that existed in those days that a dominant allele tended to naturally increase in frequency.

Applications of Hardy Weinberg Law

Below mentioned are the applications of Hardy Weinberg law:-

The confusion over selection and dominance just isn't very exceptional in today's times. The Hardy-Weinberg genotype frequency tests are currently used to determine population stratification and other forms of non-random mating.

  • Genetic variations that change from mutation, genetic drift, migration, sexual selection and natural selection are persistently reflected by natural populations. A statistical criterion for a non-evolving population that can be contrasted with evolving populations is given by the Hardy-Weinberg rule.

  • Through this period, if the allele frequencies are recorded and calculated on the basis of the Hardy-Weinberg law values for the predicted frequencies, then it is possible to hypothesize operations that drive population evolution.

  • The law provides a template that is usually used to research the population genetics of diploid organisms as a point of origin that fulfils the common argument of a large population, random mating, no mutation, selection or migration.

  • However, for haploid pathogens, the Hardy-Weinberg model is not valid. Each of the principles in this law is thus broken in the case that a population is not discovered in the Hardy Weinberg equilibrium equation. 

  • This suggests that the population has been affected by selection, migration or non-random mating, where studies are taken out and theories are pursued in order to understand the mechanism behind its population's non-equilibrium.

Linkage Disequilibrium

Consider, for example, two or more alleles on the common chromosome, with 2 or more alleles in two separate loci. The frequency of allelic combinations reaches equilibrium as a consequence of genetic exchange through recombination occurring at regular intervals of time, across two syntenic loci.

Alleles are considered to be in a linkage disequilibrium if they are unable to reach an equilibrium, which is attributable to the inheritance of two or more connected alleles jointly, rather frequently than expected. These gene classes are known as supergenes as well.

Complete Dominance

In the case of total dominance, allele frequencies can be identified when Hardy-Weinberg equilibrium persists, where it would not be possible to distinguish among two genotypes. As a consequence of complete dominance of R over r, two genotypes RR and Rr sharing the same phenotype will help in deciding the allele frequencies from individual frequencies showing recessive phenotype rr. Here, the frequency of an individual should be equal to the frequency square of the recessive allele.

Significance of Hardy Weinberg Law

The significance of Hardy Weinberg law is that the model helps to evaluate the real genetic structure of a population over time. Only with the genetic composition, we would predict if the population was in equilibrium with Hardy-Weinberg (i.e., not evolving).

In evaluating the genetic variation present in a population, Hardy Weinberg law is essential and compares the real variation to the calculated value of Hardy Weinberg law if the population was in equilibrium. If the real frequency in a population varies from the predicted value, then it is an indicator of one or more assumptions being disrupted and violated, which can be further investigated. It also helps in predicting the prevalence of a negative recessive gene in the heterozygous carriers.

FAQ (Frequently Asked Questions)

Q1. Give the Assumptions of Hardy–Weinberg Equilibrium.

Ans. The following are the seven assumptions underlying the Hardy-Weinberg equilibrium:

  • organisms tend to be diploid

  • only sexual reproduction takes place

  • generations are found to be non-overlapping

  • mating tends to be random.

  • population size is extremely large.

  • In all the sexes, allele frequencies are equivalent.

  • There occurs no gene flow, migration, admixture, selection or mutation.

Q2. How does Mutation Affect Hardy Weinberg?

Ans. In the gene sequence of DNA, mutations are irreversible changes. These modifications change genes and alleles that contribute to a population's genetic variation. While mutations cause changes in a population's genotype, they might or might not produce changes that are detectable or phenotypic. Specific genes or whole chromosomes could be affected by mutations. 

The lack of mutations in a population is among the conditions which must be fulfilled for the Hardy-Weinberg equilibrium. These modifications change genes and alleles that contribute to a population's genetic variation.