Species: a group of similar organisms that can reproduce to give fertile offspring

Population: A group of organisms of the same species living in a particular area at a particular time

Gene Pool: Complete range of alleles present in a population

Allele Frequency: The frequency of an allele in a population (given as a %)

Hardy-Weinberg Principle

  • Used to predict the frequencies of alleles/genotype/phenotype within a population
  • It can also be test whether or not the Hardy-Weinberg principles applies to a particular allele in a particular population
    • E.g. if frequencies do change between generations in a large population then there’s an influence of some kind
  • The principle will work providing:
    • Large Population size
    • No immigration/Emigration
    • No natural selection
    • Random mating (so all possible genotypes can bread with all others)

Allele Frequency

p + q = 1

p = Frequency of one allele (usually dominant)

q = frequency of one different allele (usually recessive)

  • the frequencies of both p and q must equal to 1 (100%)

Genotype Frequency

p2 + 2pq + q2 = 1

p2 Frequency of homozygous dominant genotype

2pq = Frequency of heterozygous genotype

q2 = Frequency of homozygous recessive genotype

  • Total frequency of all genotypes within a population = 1 (100%)
  • Phenotype can also be determine providing that the relation between phenotype and genotype is known
  • Principle can also be used if two alleles are codominant or if whether the allele is recessive and which is dominant is unknown
    • By making p represent one allele and q represent the other