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  2. Fixation (population genetics) - Wikipedia

    en.wikipedia.org/wiki/Fixation_(population_genetics)

    In the absence of mutation or heterozygote advantage, any allele must eventually either be lost completely from the population, or fixed, i.e. permanently established at 100% frequency in the population. [2] Whether a gene will ultimately be lost or fixed is dependent on selection coefficients and chance fluctuations in allelic proportions. [3]

  3. Fixed allele - Wikipedia

    en.wikipedia.org/wiki/Fixed_allele

    In population genetics, a fixed allele is an allele that is the only variant that exists for that gene in a population. A fixed allele is homozygous for all members of the population. [1] The process by which alleles become fixed is called fixation. For this hypothetical species, the population in the topmost frame exhibits no fixed allele for ...

  4. Scientific theory - Wikipedia

    en.wikipedia.org/wiki/Scientific_theory

    A scientific theory differs from a scientific fact or scientific law in that a theory seeks to explain "why" or "how", whereas a fact is a simple, basic observation and a law is an empirical description of a relationship between facts and/or other laws.

  5. Population genetics - Wikipedia

    en.wikipedia.org/wiki/Population_genetics

    Population genetics is a subfield of genetics that deals with genetic differences within and among populations, and is a part of evolutionary biology.Studies in this branch of biology examine such phenomena as adaptation, speciation, and population structure.

  6. Bateson–Dobzhansky–Muller model - Wikipedia

    en.wikipedia.org/wiki/Bateson–Dobzhansky...

    For example, an ancestral species has the alleles a and b fixed in its population, resulting in all individuals having the aabb genotype. When two descendant populations are separated from each other and each undergo several mutations the allele A can occur in one population while the allele B occurs in the second population.

  7. Selective sweep - Wikipedia

    en.wikipedia.org/wiki/Selective_sweep

    In genetics, a selective sweep is the process through which a new beneficial mutation that increases its frequency and becomes fixed (i.e., reaches a frequency of 1) in the population leads to the reduction or elimination of genetic variation among nucleotide sequences that are near the mutation.

  8. Genetic drift - Wikipedia

    en.wikipedia.org/wiki/Genetic_drift

    Once an allele becomes fixed, genetic drift comes to a halt, and the allele frequency cannot change unless a new allele is introduced in the population via mutation or gene flow. Thus even while genetic drift is a random, directionless process, it acts to eliminate genetic variation over time.

  9. Coalescent theory - Wikipedia

    en.wikipedia.org/wiki/Coalescent_theory

    Coalescent theory is a model of how alleles sampled from a population may have originated from a common ancestor. In the simplest case, coalescent theory assumes no recombination , no natural selection , and no gene flow or population structure , meaning that each variant is equally likely to have been passed from one generation to the next.

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