Evolutionary Change

Evolutionary Change

Calculation of Allele and Genotype Frequencies & Hardy-Weinberg Equilibrium Theory



Introduction

Population geneticists frequencies of genotypes and alleles inside populations other than the ratios of phenotypes that Mendelian geneticists use. (Crow 1999) By matching these frequencies with those forecast by null models that suppose no evolutionary means are portraying inside populations? they draw deductions considering the evolutionary forces in operation. In a unchanging environment? genes will extend to sort likewise for generations upon generations. (Edwards 1977) The fact of this constancy directed two investigators? G. Hardy and W. Weinberg? to articulate an significant relationship in evolution. The law that recounts this relationship bears their names.

 

Discussion

The Hardy-Weinberg Equilibrium Theory serves as the rudimentary null form for population genetics. Every one-by-one has alleles that were passed on from their parents. (Guo 1992) If we take all of the alleles of a group of individuals of the identical species (that is? a population) we have what is called the gene pool. The frequency? or percentage? of individuals in that population that own a certain allele is called the allele frequency. Populations could have allele frequencies? but individuals cannot. This conspicuously makes populations the best hierarchical unit? or grade? to study evolution? as evolution is fundamentally the study of the change in allele frequencies over time.

 

Allele Frequencies

Consider an one-by-one locus and a population of diploid individuals where two distinct alleles A and a could be discovered at that locus. If your population comprises of 100 individuals? then that group possesses 200 alleles for this locus (100 individuals x 2 alleles at that locus per individual). (Crow 1999) The number of A alleles present in that population conveyed as a fraction of all the alleles (A or a) at that locus comprises the frequency of the A allele in population.

To calculate allele frequencies for populations of diploid organisms? first multiply the number of individuals in population by 2 to get the total number of alleles at that locus.

Select one of the alleles for your first set of calculations. Let's first select the A allele from the demonstration supplied above.

a. Individuals homozygous for the A allele will each own 2 A alleles. Multiply the number of AA homozygotes by 2 to calculate the number of A alleles.

b. Heterozygotes will each own only one A allele.

c. The total number of A alleles in population = [(the number of Aa heterozygotes) + (2 x the number of AA homozygotes)]

The frequency of the A allele = [(total number of A alleles in population) / (total number of alleles in population for that locus)]

The frequency of the allele = (1 - frequency of the A allele) Genotype Frequencies address the identical population? locus? and alleles recounted above.

 

Genotype frequencies comprise the plenty of each genotype inside a population as a fraction of the population size. (Edwards 1977) In other phrases? the frequency of the AA genotype comprises the fraction of the population homozygous for the A allele.

To calculate genotype frequencies for populations of diploid ...