# hardey weinberg law

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Published on May 27, 2018

Author: Dasanal

Source: authorstream.com

HARDY WEINBERG LAW – FACTORS AFFECTING EQUILIBRIUM FREQUENCIES IN RANDOM MATING POPULATIONS: HARDY WEINBERG LAW – FACTORS AFFECTING EQUILIBRIUM FREQUENCIES IN RANDOM MATING POPULATIONS PREPARED BY.... KIRAN DASANAL [UG13AGR1879 ] INTRODUCTION: INTRODUCTION Cross-pollinated crops are highly heterozygous due to the free intermating among their plants. They are often referred to as random mating populations. Mendelian population A population, in this case, consists of all such individuals that share the same gene pool Hardy-Weinberg law: Hardy-Weinberg law The Hardy-Weinberg law is the fundamental law of population genetics and provides the basis for studying Mendelian populations. This law was independently developed by Hardy (1908) in England and Weinberg (1909) in Germany. Hardy-Weinberg law: Hardy-Weinberg law The Hardy-Weinberg law states that the gene and genotype frequencies in a Mendelian population remain constant generation after generation if there is no selection, mutation, migration or random drift. Example of Hardy-Weinberg law: Example of Hardy-Weinberg law Let us consider a single gene with two alleles, A and a, in a random mating population. There would be three genotypes, AA, Aa and aa, for this gene in the population. Suppose the population has N individuals of which D individuals are AA, H individuals are Aa and R individuals are aa. so that D +H + R = N. Cont…………: Cont………… p = (2D + H) / 2N or = (D + ½ H) / N and q = (2R + H) / 2N or = (R + ½ H) / N Therefore, p + q = 1 Such a population would be at equilibrium since the genotypic frequencies would be stable, that is, would not change, from one generation to the next. This equilibrium is known as Hardy-Weinberg equilibrium. Factors affecting equilibrium frequencies: Factors affecting equilibrium frequencies Migration: Migration Migration is the movement of individuals into a population from a different population. Migration may introduce new alleles into the population or may change the frequencies of existing alleles. In plant breeding programmes, migration is represented by intervarietal crosses , polycrosses , etc., wherein the breeder brings together into a single population two or more separate populations. Mutation: Mutation Mutation is a sudden and heritable change in an organism and is generally due to structural change in a gene . It is the ultimate source of all the variation present in biological materials. Mutation may produce a new allele not present in the population or may change the frequencies of existing alleles. Random drift: Random drift Random drift or genetic drift is a random change in gene frequency due to sampling error. Random drift occurs in small populations because sampling error is greater in a smaller population than in a larger one . The breeder cannot do anything to prevent this genetic drift, except to use very large populations. Inbreeding: Inbreeding Mating between individuals sharing a common parent in their ancestry is known as inbreeding. Inbreeding reduces the proportion of heterozygotes or heterozygosity and increases the frequency of homozygotes or Homozygosity. Selection: Selection Differential reproduction rates of various genetypes is known as selection . The breeder is able to improve the various characteristics by selecting for the desirable types. In a random mating population. selection is expected to change gene frequencies rather than to eliminate one or the other allele. THANK YOU: THANK YOU

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