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Allele. An allele[1], or allelomorph, is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule. [2] Alleles can differ at a single position through single nucleotide polymorphisms (SNP), [3] but they can also have insertions and deletions of up to several thousand base pairs. [4]
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 (allele) in a population due to random chance. [ 2 ] Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. [ 3 ]
Paramutation. In epigenetics, a paramutation is an interaction between two alleles at a single locus, whereby one allele induces a heritable change in the other allele. [1] The change may be in the pattern of DNA methylation or histone modifications. [2] The allele inducing the change is said to be paramutagenic, while the allele that has been ...
Allele frequency. Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. [1] Specifically, it is the fraction of all chromosomes in the population that carry that allele over the total population or sample size.
In population genetics, fixation is the change in a gene pool from a situation where there exists at least two variants of a particular gene (allele) in a given population to a situation where only one of the alleles remains. That is, the allele becomes fixed. [1] In the absence of mutation or heterozygote advantage, any allele must eventually ...
Genetics is the study of genes and tries to explain what they are and how they work. Genes are how living organisms inherit features or traits from their ancestors; for example, children usually look like their parents because they have inherited their parents' genes. Genetics tries to identify which traits are inherited and to explain how ...
Bottom (Graph 3) represents disruptive selection with both extremes being favored. In population genetics, directional selection is a type of natural selection in which one extreme phenotype is favored over both the other extreme and moderate phenotypes. This genetic selection causes the allele frequency to shift toward the chosen extreme over ...
Gene conversion. 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.