Population Genetics

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Phenotypic variation in populations

Genetic variation in populations

Allele frequencies:

allele frequency: the proportion of a certain allele within a population.

Fact: allele frequency = gene frequency = gametic frequency

gene pool: the set of all alleles at all loci in a population.

The Hardy-Weinberg genetic equilibrium:

The allele and genotypic frequencies remain the same from generation to generation in a population in which there is

Moreover, the equilibrium genotype frequencies are given by

p2: the frequency of the homozygous dominant genotype

2pq: the frequency of the heterozygous genotype

q2: the frequency of the recessive genotype.

Frequencies for some alleles can be very close to the equilibrium
values, such as in the case of the MN alleles in humans.

Processes Causing Deviations from the Hardy-Weinberg Equilibrium

evolution: changes in allele frequencies in a population.

As a result of the above forces operating on populations, genetic and phenotypic differences emerge and accumulate over time. This process, called differentiation, leads ultimately to the emergence of new forms, races and species.
For further discussion on speciation, see Macroevolution.

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