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Antigenic shift is a specific case of reassortment or viral shift that confers a phenotypic change. Antigenic shift is contrasted with antigenic drift , which is the natural mutation over time of known strains of influenza (or other things, in a more general sense) which may lead to a loss of immunity, or in vaccine mismatch.
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 ]
This is known as the standard reading frame. However, in cases of frame shift mutations, an extra nucleotide (or more) is inserted into the DNA sequence, disrupting the typical reading frame and causing a shift in the sequence. This insertion prompts a shift in the reading frame due to the triplet nature of the genetic code.
Antigenic shift is a closely related process; it refers to the more dramatic changes in the virus's surface proteins when the genetic material from two or more viruses mix together. Genetic drift is very different and much more broadly applicable; it refers to the gradual accumulation in any DNA sequence of random mutational changes that do not ...
Spontaneous de novo mutations as cataclysmic events of speciation depend on factors introduced by natural selection, genetic flow, and genetic drift. For example, smaller populations with heavy mutational input (high rates of mutation) are prone to increases of genetic variation which lead to speciation in future generations.
Genetic drift allows a locally adapted subpopulation to move across an adaptive valley to the base of a higher adaptive peak. Natural selection will move the subpopulation up the higher peak. This new superiorly adapted subpopulation may then expand its range and outcompete or interbreed with other subpopulations, causing the spread of new ...
In population genetics, gene flow (also known as migration and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be considered a single effective population.
Early work used a “shift model” in which can vary between generations but the mean fitness of the population is reset to zero after fixation. This basically assumes the distribution of is constant (in this sense, the argument in the previous paragraphs can be regarded as based on the “shift model”). This assumption can lead to ...