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  2. Balancing selection - Wikipedia

    en.wikipedia.org/wiki/Balancing_selection

    Balancing selection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone. Balancing selection is rare compared to purifying selection. [1]

  3. Directional selection - Wikipedia

    en.wikipedia.org/wiki/Directional_selection

    Three different types of genetic selection. On each graph, the x-axis variable is the type of phenotypic trait and the y-axis variable is the amount of organisms. Group A is the original population and Group B is the population after selection. Top (Graph 1) represents directional selection with one extreme favored.

  4. Stabilizing selection - Wikipedia

    en.wikipedia.org/wiki/Stabilizing_selection

    Stabilizing selection (not to be confused with negative or purifying selection [1] [2]) is a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value. This is thought to be the most common mechanism of action for natural selection because most traits do not appear to change drastically over time ...

  5. Disruptive selection - Wikipedia

    en.wikipedia.org/wiki/Disruptive_selection

    These charts depict the different types of genetic selection. On each graph, the x-axis variable is the type of phenotypic trait and the y-axis variable is the amount of organisms. Group A is the original population and Group B is the population after selection. Graph 1 shows directional selection, in which a single extreme phenotype is favored.

  6. Frequency-dependent selection - Wikipedia

    en.wikipedia.org/wiki/Frequency-dependent_selection

    In negative frequency-dependent selection, the fitness of a phenotype or genotype decreases as it becomes more common. This is an example of balancing selection. More generally, frequency-dependent selection includes when biological interactions make an individual's fitness depend on the frequencies of other phenotypes or genotypes in the ...

  7. Heterozygote advantage - Wikipedia

    en.wikipedia.org/wiki/Heterozygote_advantage

    Polymorphism can be maintained by selection favoring the heterozygote, and this mechanism is used to explain the occurrence of some kinds of genetic variability. A common example is the case where the heterozygote conveys both advantages and disadvantages, while both homozygotes convey a disadvantage.

  8. Hardy–Weinberg principle - Wikipedia

    en.wikipedia.org/wiki/Hardy–Weinberg_principle

    While directional selection eventually leads to the loss of all alleles except the favored one (unless one allele is dominant, in which case recessive alleles can survive at low frequencies), some forms of selection, such as balancing selection, lead to equilibrium without loss of alleles.

  9. Mutation–selection balance - Wikipedia

    en.wikipedia.org/wiki/Mutation–selection_balance

    Nevertheless, the concept is still widely used in evolutionary genetics, e.g. to explain the persistence of deleterious alleles as in the case of spinal muscular atrophy, [5] [4] or, in theoretical models, mutation-selection balance can appear in a variety of ways and has even been applied to beneficial mutations (i.e. balance between selective ...