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Evolutionary pressure, selective pressure or selection pressure is exerted by factors that reduce or increase reproductive success in a portion of a population, driving natural selection. [1] It is a quantitative description of the amount of change occurring in processes investigated by evolutionary biology , but the formal concept is often ...
Gene flow is the transfer of alleles from one population to another population through immigration of individuals. 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 ...
Regulation of gene expression, or gene regulation, [1] includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are widely observed in biology, for example to trigger developmental pathways, respond to environmental ...
Fixation rates can easily be modeled as well to see how long it takes for a gene to become fixed with varying population sizes and generations. For example, The Biology Project Genetic Drift Simulation allows to model genetic drift and see how quickly the gene for worm color goes to fixation in terms of generations for different population sizes.
In this form of phase variation. The promoter region of the genome can move from one copy of a gene to another through homologous recombination. This occurs with Campylobacter fetus surface proteins. The several different surface antigen proteins are all silent apart from one and all share a conserved region at the 5' end.
Gene flow is the exchange of genes between populations or species, breaking down the structure. Examples of gene flow within a species include the migration and then breeding of organisms, or the exchange of pollen. Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer. Population genetic models ...
There are various combinations of regulation involving pathogenicity islands. The first combination is that the pathogenicity island contains the genes to regulate the virulence genes encoded on the PAI. [2] The second combination is that the pathogenicity island contains the genes to regulate genes located outside of the pathogenicity island. [2]
Reduced gene flow between central and peripheral populations also limits the genetic diversity at the margins. High selection pressure, due to a less than ideal habitat at the margin, furthermore reduces genetic diversity. Although exceptions to this hypothesis are common, in general this rule appears to hold empirically true.