Gene Pools

• Gene Pools


  The sum of alleles carried by individuals in a genetic population
• Alleles


  Alternative form of a gene that are found in the same place on a chromosome
• Genetic Variation


  The variation in the DNA sequences in each of our genomes
• Changes in allele frequency caused by

  • Mutations
  • Differing selection pressures
• Differing selection pressures


  • Natural selection affecting survival & reproduction
  • Includes competition, predation and environment
  • Alleles are selected for or against
• Natural selection affects survival and reproduction
• Alleles are selected for or against, either removing or keeping mutations in the population
• Different environmental pressures result in different alleles being selected for
• Over time, allele frequencies in the gene pools will change where populations become less like each other depending on which alleles are selected for
• Random Genetic Drift


  The change in allele frequency in a population due to chance events that are non-directional
• Random events affect small populations more than large
• Founder Effect


  When a small group moves away from their homeland to a new area to establish a new community
• Founder Effect


  • Islanders
• New people from the population carry the new allele frequency into the new population
• Small population is not representative of the larger population
• Changes in allele frequencies in a gene pool due to

  • Migration
  • Gene Flow
• Gene Flow


  Transfer of alleles from one population to another population through migration
• Individuals migrate to new areas
• Migrants may have alleles that are not present in the original population before arrival
• Immigration


  Into a population
• Emigration


  Out of a population
• Barriers to Gene Flow

  • Isolation contributes to the development of separate gene pools
  • Different environmental pressures result in different characteristics being favoured
  • Over many generations the allele frequencies change, resulting in the separated gene pools, inhibiting interbreeding
  • Geographical barriers: oceans, mountain ranges, lakes and deserts
  • Sociocultural barriers: culture/language/economic status/educational background/religion/founder effect/environmental pressures