A gene pool represents the sum total of alleles for all genes present in a sexually reproducing population

• A large gene pool indicates high amounts of genetic diversity, increasing the chances of biological fitness and survival

• A small gene pool indicates low amounts of genetic diversity, reducing biological fitness and increasing chances of extinction
  

As each individual contains two alleles for each gene (diploid), the number of alleles in a gene pool should be twice the population size

• Gene pools can be used to determine allele frequency – the proportion of a particular allele within a population

Gene Pools

Allele Frequency

Allele frequency describes the prevalence of a given allele out of all of the alleles for a specific gene within a gene pool

• Allele frequency is calculated by dividing the occurrence of a specific allele by the total occurrence of all alleles for a particular gene
  

• Allele frequencies can be expressed as percentages, fractions of decimals (frequency of all alleles for a gene must equal 1)

Allele frequencies will change in a population over time (large populations with stable environments will experience less change)

• Genetic variation can occur naturally (via mutations or gene flow) to increase the genetic diversity of a population by creating new alleles
  

• Evolutionary processes (natural or artificial selection) will decrease genetic diversity as species are adapted to suit the prevailing conditions

  • Allele frequencies can also fluctuate over time due to random or chance events (genetic drift) – smaller populations are more prone to drift

When two populations are geographically isolated and unable to exchange alleles (no gene flow), differences will emerge in the frequency of particular alleles

• The most common type of genetic variation within a population are single nucleotide polymorphisms (SNPs) – which are derived from a single base substitution
  

Allele frequencies in human populations can be compared using online databases to provide information for scientific endeavours

• Medical clinicians can use allele frequencies to identify genetic associations with particular diseases (and assess predispositions)

• Epidemiologists can use allele frequencies to determine levels of viral resistance in populations and map disease spread

• Anthropologists can use allele frequencies to trace evolutionary lineages and construct cladograms via phylogenetic analysis

Comparing Allele Frequencies