Hardy-Weinberg Principle

Introduction

Hardy-Weinberg Theorem apply only when the populace conforms to the subsequent assumptions: The natural choice isn’t appearing at the locus in question .Neither mutation (the starting place of the latest alleles) nor migration (the motion of people and their genes into or out of the populace) is introducing new alleles into the population. But before we start discussing our main topic, we will define some of the key terms used in this article. 

Key terms  

1. Allele- An allele refers to one or more versions or forms of a gene. Originally, the term ‘allele’ was used to describe variation in genes; however, currently, the term refers to variations in the form of versions among non-coding DNA sequences. People inherit one allele from each parent, and biologists lump alleles into categories. Therefore, their alleles are normal, wild-type, abnormal, or mutant.  
2. Allele Frequency of Gene Frequency- Allele frequency refers to the frequency in which a certain type of allele appears within a population. The Hardy-Weinberg equation calculates the frequency of alleles (number of individual alleles of a certain type within a population). 
3. Genotype- While there is a large amount of common DNA amongst most humans, there is variation in the sequence of the DNA amongst individuals. Genotype describes the version of the DNA sequence an individual has. Genotype refers to the two types of alleles inherited for a particular gene. The information encoded in a gene’s DNA and used to make protein expresses the genotype. 
4. Homozygous- Homozygous is a genetic condition where a person has inherited the same alleles for a particular gene from their biological father and mother. Homozygous describes the genetic state where an individual has inherited the same DNA sequence for a particular gene from their biological parents. Individuals can either possess dominant or recessive alleles. 
5. Diploid- A diploid describes a cell or an organism that acquires pairs of chromosomes from each parent. 
6. Genetic Drift- Genetic drift refers to fluctuations in the allele frequencies at random. 
7. Genetic recombination refers to the exchange of genetic material between different regions within the same chromosome or between two different chromosomes. Genetic recombination increases genetic diversity amongst sexually reproducing organisms. 

Evolution

Evolution refers to the biological process that explains the development of different kinds of living organisms from other living organisms during the earth’s history. There are four major ways in which evolution takes place. These are convergent evolution, divergent evolution, parallel evolution, and coevolution. 

Hardy Weinberg principle 

• We can simply explain Hardy Weinberg’s principle by defining it as a principle which states in the absence of disturbing factors, the genetic variation in a population will remain constant
• The Hardy Weinberg principle believes that in the absence of disturbing factors when mating is non-random, the allele frequency and genotype of the population will remain stable and constant because it is in equilibrium
• According to the principle, the conditions for equilibrium are- 

1. No mutation shall occur. Since no mutation occurs, no new alleles are being created. 
2. There shall be no migration. No population shall either enter or leave the population. 
3. The population in question is large. 
4. Individuals don’t choose their mates based on genotype, and therefore, mating is performed at random. 
5. Every individual in the population has an equal opportunity to procreate as there is no natural selection. 

• When the assumptions mentioned above are violated, they will cause the following changes to the gene pool

• Natural selection can cause changes to the allele frequency. Selection can lead to the loss of all alleles except the favored ones 
• Two or more populations get linked to each other via migration. This increases the homogeneity amongst allele frequencies, making the Hardy Weinberg principle invalid
• Genetic drift within small populations can cause random changes in the allele frequencies

• Genetic drift, mutation, natural selection, non-random mating and gene flow can disrupt the equilibrium stated under the Hardy Weinberg principle by introducing new genes and alleles in the gene pool
• All evolution would have to stop for the equilibrium mentioned in the Hardy Weinberg principle to come true. 

Hardy Weinberg equation

The Hardy-Weinberg equation is as follows- 

1 = p2 + 2pq + q2

Where p and q represent the frequency of different types of alleles. 

p2 = frequency of homozygous dominant genotype. 

q2 = frequency of homozygous recessive genotype. 

This equation is used to calculate the frequency of alleles. 

The evolutionary change had occurred when the allele frequency measured differed from the expected values. The range of the difference indicates the extent of the evolutionary change. Change in allele frequencies or disturbance in the genetic equilibrium results in evolution. 

Applications of the Hardy Weinberg principle 

1. The Hardy Weinberg principle provides a mathematical criterion to compare evolving populations with non-evolving populations. 
2. Scientists can determine the mechanisms that drive the human population’s evolution by comparing the allele frequency over time with the expected frequencies based on Hardy-Weinberg values. 
3. Due to genetic drift, mutation, migration, and natural and sexual selections, the genetic variation of natural populations is constantly evolving. And scientists can hypothesize what is driving evolution with the help of the Hardy Weinberg principle. 

G.H Hardy and Wilhelm Weinberg

• Godfrey Harold Hardy was a prolific English mathematician known for his number theory, biology, and mathematical analysis. Hardy was also the mentor and close collaborator of Srinivasa Ramanujan

• Wilhelm Weinberg was a German obstetrician-gynecologist. Weinberg, independent of British mathematician G.H Hardy, developed the principle of genetic equilibrium in 1908
• Wilhelm Weinberg expressed his concept in ‘The Annals of the Society of National Natural History in Wurttemberg,’ which was published in 1908, months before G.H. Hardy’s notes would be published
• For several years, people in the English-speaking world were unaware of Weinberg’s contributions, and the concept of genetic equilibrium had been known as ‘Hardy’s Law.’ However, Curt Stern, who lived in the United States, pointed out Weinberg’s contributions were more comprehensive than Hardy’s

Conclusion

The conclusions of the Hardy-Weinberg Theorem apply only when the populace conforms to the subsequent assumptions: The natural choice isn’t appearing at the locus in question .Neither mutation (the starting place of the latest alleles) nor migration (the motion of people and their genes into or out of the populace) is introducing new alleles into the populace. Population length is infinite.