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Related Experiment Videos

The evolution of one- and two-locus systems

T Nagylaki

    Genetics
    |July 1, 1976
    PubMed
    Summary
    This summary is machine-generated.

    Under weak selection, population genetics models show that deviations from Hardy-Weinberg proportions and linkage equilibrium have minimal evolutionary impact. Genotypic frequencies evolve predictably, with changes in mean fitness closely mirroring genic variance over time.

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    Area of Science:

    • Population Genetics
    • Evolutionary Biology
    • Mathematical Biology

    Background:

    • Investigates population genetics models under weak natural selection.
    • Assumes age-independent fertilities and mortalities with random mating in a monoecious population.
    • Considers models with a single locus (multiple alleles) and two loci (two alleles each).

    Purpose of the Study:

    • To analyze the behavior of population genetics models under weak selection.
    • To determine the significance of deviations from Hardy-Weinberg proportions and linkage equilibrium.
    • To derive new expressions for the change in mean fitness.

    Main Methods:

    • Employs continuous-time models and discrete non-overlapping generation models.
    • Utilizes a slow-selection analysis where selective differences change at most as O(s^2).

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  • Examines the rate of change of deviations from Hardy-Weinberg proportions and linkage disequilibrium.

    • Main Results:

    • Deviations from Hardy-Weinberg proportions and linkage disequilibrium change at a rate of O(s^2).
    • To O(s^2), the rate of change of mean fitness equals the genic variance, provided fitness changes are o(s^2).
    • Genotypic frequencies evolve approximately as if in Hardy-Weinberg proportions and linkage equilibrium, with an error of O(s).

    Conclusions:

    • Deviations from random mating have minimal evolutionary significance for the deterministic behavior of one and two loci.
    • The rate of change of mean fitness can occasionally decrease, particularly near equilibrium when allelic frequencies change slowly.
    • New expressions for the change in mean fitness were derived, offering insights into population evolutionary dynamics.