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Through natural selection and random genetic drift, the traits with a negative effect on population fitness disappear from the gene pool. The balance between the influence of natural selection and genetic drift on the population mutation rate is mainly determined by the population size. [5]
Genetic variation is the difference in DNA among individuals [1] or the differences between populations among the same species. [2] The multiple sources of genetic variation include mutation and genetic recombination. [3] Mutations are the ultimate sources of genetic variation, but other mechanisms, such as genetic drift, contribute to it, as ...
The Nearly neutral theory stems from the prediction of neutral theory that the balance between selection and genetic drift depends on effective population size. [29] Nearly neutral mutations are those that carry selection coefficients less than the inverse of twice the effective population size. [30]
Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, [1] is the change in the frequency of an existing gene variant in a population due to random chance. [ 2 ] Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation . [ 3 ]
Tajima's D is a population genetic test statistic created by and named after the Japanese researcher Fumio Tajima. [1] Tajima's D is computed as the difference between two measures of genetic diversity: the mean number of pairwise differences and the number of segregating sites, each scaled so that they are expected to be the same in a neutrally evolving population of constant size.
Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion. [1] Gene conversion can be either allelic, meaning that one allele of the same gene replaces another allele, or ectopic, meaning that one paralogous DNA sequence converts another.
This process is often characterized by a description of the starting and ending states, or the kind of change that has happened at the level of DNA (e.g,. a T-to-C mutation, a 1-bp deletion), of genes or proteins (e.g., a null mutation, a loss-of-function mutation), or at a higher phenotypic level (e.g., red-eye mutation).
In this theory, every evolutionary event, mutation, and gene polymorphism (neutral differences in phenotype or genotype) would have to be positively or negatively selected for and show some kind of change over many generations. [3] If these genetic differences grow between different populations speciation events can occur.