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In evolutionary biology, disruptive selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into two distinct groups.
A mechanism of sex determination that depends upon the ratio of the number of X chromosomes (X) to the number of sets of autosomes (A). Males develop when the X/A ratio is 0.5 or less, females when it is 1.0 or more, and an intersex develops when it is between 0.5 and 1.0. [8] genic selection
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
The resulting influx of deleterious mutations into a population over time is counteracted by negative selection, which acts to purge deleterious mutations. Setting aside other factors (e.g., balancing selection , and genetic drift ), the equilibrium number of deleterious alleles is then determined by a balance between the deleterious mutation ...
Stabilizing selection conserves functional genetic features, such as protein-coding genes or regulatory sequences, over time by selective pressure against deleterious variants. [105] Disruptive (or diversifying) selection is selection favoring extreme trait values over intermediate trait values.
X hyperactivation refers to the process in Drosophila by which genes on the X chromosome in male flies become twice as active as genes on the X chromosome in female flies. Because male flies have a single X chromosome and female flies have two X chromosomes, the higher level of activation in males ensures that X chromosome genes are overall ...
A refractory gene alone would not have higher fitness than the native genes, but engineered underdominance may prove effective as a mechanism to spread such a gene. In this model, two genetics constructs are introduced into two non-homologous chromosomes. Each construct is lethal when expressed individually but can be suppressed by the other ...
Balancing selection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone. Balancing selection is rare compared to purifying selection. [1]