Canalisation (genetics) 3557327 202379154 2008-03-31T20:45:54Z Guest9999 3486857 add evolution navigational template [[Image:Trait-scale-bimodal.png|thumb|right|313px|[[Norms of reaction]] for two genotypes. Genotype B shows a strongly bimodal distribution indicating differentiation into distinct phenotypes. Each phenotype is buffered against environmental variation - it is canalised.]] '''Canalisation''' ('''canalization''' in [[American English]]) is a measure of the ability of a [[population]] to produce the same [[phenotype]] regardless of variability of its environment or [[genotype]]. The term '''canalisation''' was coined by [[C. H. Waddington]], who also helped explain its developmental mechanisms. He also introduced the [[epigenetic landscape]], in which a canalised trait is illustrated as a valley enclosed by high ridges, safely guiding the phenotype to its "fate". Canalisation is divided into genetic and environmental canalisation; genetic canalisation refers to distinct genotypes producing the same phenotype, while environmental canalisation refers to the same genotype producing the same phenotype in spite of environmental variation. A recent molecular example was given by Rutherford & Lindquist.<ref>{{cite journal| title=Hsp90 as a capacitor for morphological evolution| journal=[[Nature (journal)]] | year=1998|volume=396 |pages=336 |author=Rutherford SL, Lindquist S.}}</ref> [[Hsp90]] is a [[Chaperone (protein)|chaperone]] protein, monitoring the correct folding of some polypeptides into proteins. Rutherford & Lindquist [[heat shock]]ed [[drosophila]] embryos, therefore recruiting a vast proportion of cytoplasmic Hsp90 to respond to the stress. The decrease in the normal monitoring activity of Hsp90 resulted in many morphological changes in the adult flies. These changes would disappear at the next generation in the absence of the stress. One possible conclusion is that Hsp90 is buffering mutations: flies have accumulated many mutations, but their effect is suppressed by Hsp90. To test this hypothesis, they crossed flies displaying morphological changes, mimicking natural selection during big environmental changes. The resulting flies displayed morphological changes even in the absence of heat shock : the amount of accumulated mutations in these flies had overcome the buffering capacity of Hsp90 and these flies had changed their epigenetic valley. This, then, is an example of genetic canalisation. ==References== <references/> ==See also== *[[Developmental biology]] ==External links== *[http://www.cbc.yale.edu/old/cce/papers/Canal/Canal.html Abstract of A Population Genetic Theory of Canalization, by Günter P. Wagner, Ginger Booth, and Homayoun Bagheri-Chaichian] <br style="clear:both;" /> {{genarch}} {{Evolution}} [[Category:Genetics]] {{genetics-stub}} [[es:Canalización (genética)]]