Evolution and Hardy Weinberg Principle

Hardy-Weinberg principle integrates the ideas of Mendelian genetics with Darwinian evolution by analyzing population genetics. A stable, idealized population's constant frequency of alleles and genotypes is described by the Hardy-Weinberg equilibrium principle. 

• Let’s assume that sexual reproduction in this population occurs at random, without the usual forces of evolution like mutation, natural selection, or genetic drift. 
• Without these forces of evolution, the population would stabilize in a single generation and hold that stability across succeeding generations. 
• The Hardy-Weinberg principle highlights characteristics that might affect evolution in real-world populations by specifying specified ideal circumstances under which a population would not evolve. 
• If a population is not in an equilibrium condition, at least one evolutionary factor is driving the population's change. 
• The factors affecting the shifting population can be identified with more research.

Key Terms: Evolution, Genetics, Population Genetics, Alleles, Hardy Weinberg principle.

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What is Evolution?

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As a result of natural selection, the traits of a species of plants, animals, and other living things on Earth evolve from generation to generation, according to the scientific hypothesis known as evolution. 

• During reproduction, the genes are transferred from parents to children. 
• Different characteristics appear in a certain group of animals as a result of genetic diversity or mutation. 
• Over time, certain characteristics in a particular group of species tend to become more or less frequent.

Read More: Darwin's Contributions - Theory of Evolution

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Population Genetics

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The study of variation within groups of people and the factors that influence it is known as population genetics. This entails researching how genetic variation frequencies in populations vary through time and space.

• Natural population variation is influenced by a number of primary factors, including mutation, selection, migration, and random genetic drift. 
• When a novel mutation appears, it could be advantageous for the organism, destructive, or have no influence on the fitness of the organism. 
• Natural selection often results in increases and declines in the allele frequency of advantageous and harmful mutations, respectively.
• Random genetic drift also affects allele frequencies. 
• The random variation in allele frequencies from generation to generation brought on by independent assortment in meiosis is explained by this mechanism. 
• The main influence on neutral varieties is this.
• Genome-scale data are increasingly used in modern population genetics. 
• The field is highly broad and has several applications.

Read More: Acquired and Inherited Traits

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Hardy Weinberg Principle

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The occurrence and consistency of gene frequency for a certain gene are explained mathematically by this principle. The principle stated mainly two assumptions:

1. A population's allele frequencies won't fluctuate from generation to generation.
2. When p is the frequency of the dominant allele and q is the frequency of the recessive allele for the relevant gene, the Hardy-Weinberg equation is written as p² + 2pq + q² = 1. Each of the three potential diploid genotypes' projected frequency is represented by an expression in the equation. P², Q², and 2pq stand for homozygous dominant, homozygous recessive, and heterozygous frequencies, respectively. 

• Since the entire population had been separated into the three categories that were accessible, it makes logical that if these frequencies are added up, they equal one. 
• The two alleles can also be used to define the population or gene pool, regardless of how they are packed into diploid organisms. 
• In order for the population's frequencies of the dominant and recessive alleles to sum up to 1, the equation is written as p + q = 1. 
• Again, this makes it logical given that there are only two possible alleles in the model. 
• As (p + q)² = p² + 2pq + q², it should be noted that the frequency of genotypes in the population is just the quadratic expansion of the frequency of alleles in the population.

Read More: Difference between Darwinism and Lamarckism

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Assumptions of Hardy Weinberg Principle

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The Hardy-Weinberg equilibrium equations use the following assumptions: 

1. Only sexual reproduction is possible in order to keep the balance.
2. Population members should mate at random.
3. There must be diploid organisms and a population that is infinitely huge.
4. The sex ratio must be equal, and the generations must not cross over.
5. There must be no evidence of gene flow, selection, mutation, migration, or other evolutionary impacts.

Read More: Modern Synthetic Theory of Evolution

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Applications of Hardy Weinberg Principle

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A few important applications of Hardy Weinberg principle are–

1. Complete Dominance– When Hardy-Weinberg equilibrium prevails and it is impossible to tell one genotype from another, there is a chance of finding allele frequencies even in the presence of absolute dominance. 

• If two genotypes AA and Aa share the same phenotype due to the absolute dominance of A over a, it is easy to calculate the allele frequencies from the frequencies of people with the recessive trait aa. 
• The frequency of a recessive gene should be proportional to the square of the frequency of the relevant person.

2. Frequencies of Harmful Recessive Alleles– The frequency of heterozygous carriers of negative recessive genes may also be determined using the Hardy-Weinberg Law. 

• The frequency of the genotypes AA, Aa, and aa would be p² + 2pq + q² if there were two alleles A and an at an autosomal locus with frequencies p and q in the population and p + q = 1. 
• The frequency of heterozygous carriers of the recessive gene would be 2pq and the proportion of people with the detrimental trait, such as cystic fibrosis, in the population would be q².

3. Multiple Alleles– Calculating genotypic frequencies at loci with more than two alleles, such as the ABO blood types, is possible because of the Hardy-Weinberg Law. 

• With frequencies of p, q, and r, there are three alleles: I^A, I^B, and I°. 
• This time, p + q + r = 1. 
• A population with random mating would have genotypes of (p + q + r)².

4. Linkage Disequilibrium– Think about the situation where there are two or more alleles on the same chromosome or when there are two or more alleles at two different loci.

• As a result of genetic exchange caused by recombination happening at regular intervals between two syntenic loci and occurring at two syntenic loci, the frequency of allelic combinations achieves equilibrium.

Read More: Natural Selection

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Things to Remember

• By examining population genetics, Hardy-Weinberg equilibrium combines the concepts of Mendelian genetics with Darwinian evolution.
• The Hardy-Weinberg principle identifies ideal conditions under which a population would not evolve and emphasizes variables that may influence evolution in populations in the actual world. 
• A variety of basic variables, such as mutation, selection, migration, and random genetic drift, have an impact on natural population diversity. 
• The allele frequency of beneficial and detrimental mutations often rises and falls as a result of natural selection, respectively.
• The frequency of an allele in a population won't change over time.
• The Hardy-Weinberg equation is stated as p² + 2pq + q² = 1 when p is the frequency of the dominant allele and q is the frequency of the recessive allele for the relevant gene.
• Recessive gene frequency ought should be proportional to the square of the frequency of the relevant individual.

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