3.7.2 populations

• Species

  A group of organisms that can interbreed to produce fertile offspring
• Population

  All the organisms of a particular species that live in the same place
• Gene pool

  The range of different alleles existing for a particular locus within a population
• Allele frequency

  The proportion of a certain allele within a gene pool, expressed as a decimal or percentage
• What is the Hardy-Weinberg principle?

  Allows us to estimate the frequency of alleles in a population, as well as if allele frequency is changing over time
• Hardy-Weinberg assumptions

  No mutations occur to create new alleles

  No migration in or out of the population

  No selection, so alleles are all equally passed onto the next generation

  Random mating

  Large population
• Equation for calculating allele frequency

  p + q = 1

  Where; p = frequency of the dominant allele

  q = frequency of the recessive allele
• Hardy-Weinberg equation for calculating genotype frequency 


  p2 + 2pq + q2 = 1

  Where; p2 = frequency of homozygous dominant

  2pq = frequency of heterozygous

  q2 = frequency of homozygous recessive