What affects allelic frequencies in population

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  • What affects allelic frequencies in population
    • Mutation
      • Source of new alleles which can change frequency of existing alleles by competing
    • Gene flow
      • Movement of genes into or out of a population by immigration of emigration. Population may gain/lose alleles through gene flow. Tends to reduce difference between populations as gene pools become more similar
    • Population bottleneck
      • Event that drastically reduces size of population i.e. climate change, disaster, over-hunting, disease If the population recovers, many alleles may be lost, and genetic diversity is greatly reduced
    • Genetic drift
      • Random fluctuations of allele frequencies from generation to generation that take place in small, isolated populations such as island populations.
    • Fixation of alleles
      • If the frequency of an allele ever reaches zero, it is permanently eliminated from the population. The other alleles, whose frequency is now 1, is now fixed.
      • The larger the population, the longer it takes for fixation to occur
    • Population size
    • Selective pressures
      • Increases the reproductive success of fitter genotypes, measure of relative survival and reproductive success of specific individual or genotype. Fitter individuals have increased chance of leaving more offspring e.g. malarial resistance
    • Variation
      • Genetic difference between parents and offspring or between individuals in a population, will permeable through non-isolated populations
    • Founder effect
      • Occasionally, populations start with a small number of individuals (founders), allele frequencies established by chance in a population that is started by a small number of individuals e.g. Galapagos islands


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