Êtes-vous un étudiant de l'EPFL à la recherche d'un projet de semestre?
Travaillez avec nous sur des projets en science des données et en visualisation, et déployez votre projet sous forme d'application sur Graph Search.
Concept
Directional selection
Résumé
In population genetics, directional selection, is a mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. Under directional selection, the advantageous allele increases as a consequence of differences in survival and reproduction among different phenotypes. The increases are independent of the dominance of the allele, and even if the allele is recessive, it will eventually become fixed.
Directional selection was first described by Charles Darwin in the book On the Origin of Species as a form of natural selection. Other types of natural selection include stabilizing and disruptive selection. Each type of selection contains the same principles, but is slightly different. Disruptive selection favors both extreme phenotypes, different from one extreme in directional selection. Stabilizing selection favors the middle phenotype, causing the decline in variation in a population over time.
Directional selection occurs most often under environmental changes and when populations migrate to new areas with different environmental pressures. Directional selection allows for fast changes in allele frequency, and plays a major role in speciation. Analysis on QTL effects has been used to examine the impact of directional selection in phenotypic diversification. This analysis showed that the genetic loci correlating to directional selection was higher than expected; meaning directional selection is a primary cause of phenotypic diversification, which leads to speciation.
There are different statistical tests that can be run to test for the presence of directional selection in a population. A few of the tests include the QTL sign test, Ka/Ks ratio test and the relative rate test. The QTL sign test compares the number of antagonistic QTL to a neutral model, and allows for testing of directional selection against genetic drift. The Ka/Ks ratio test compares the number of non-synonymous to synonymous substitutions, and a ratio that is greater than 1 indicates directional selection.
Source officielle
À propos de ce résultat
Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.
Proximité ontologique
Séances de cours associées (122)
Polynôme caractéristique : sélections et équations
Discute des polynômes caractéristiques, des sélections de racines réelles et des équations de tiques.
Protéine Abondance: Random Walks
Explore l'abondance des protéines comme une promenade aléatoire et le modèle Moran en génétique des populations.
Composants: Roulement à billes
Explore la sélection et l'utilisation des composants, en se concentrant sur les roulements à billes et leurs types, matériaux et assemblage.
Publications associées (182)