Population Genetics

Gene pool: refers to the collection of all alleles of all genes present in a population at a specific time.

Differences:

• The gene pool of the same population can change over time due to factors like mutations, gene flow, non-random mating, natural selection, etc.

• Gene pools of different populations can differ due to factors such as geographic origin, habitat, reproductive conditions, etc.

Characteristics of the gene pool:

• Allele frequency: calculated by dividing the number of that allele by the total number of alleles in the population. Allele frequency varies depending on each population at each time, therefore it is an important characteristic to evaluate the change of the gene pool.

• Genotype frequency: calculated by dividing the number of individuals with that genotype by the total number of individuals in the population.

Self-pollination and close breeding:

• Close breeding or self-pollination gradually reduces the proportion of heterozygous genotypes and increases the proportion of homozygous genotypes.

• After multiple generations of self-pollination or close breeding, the population will gradually differentiate into pure lines with different genotypes.

• However, the process of self-pollination or close breeding does not affect the allele frequency of the population.

Number of genotypes:

• If gene A has n alleles then:

• Number of homozygous genotypes: n

• Number of heterozygous genotypes: nC2 (combination of 2 in n)

• Total number of genotypes: n(n+1)/2