Genotype-phenotype distinction
The genotypean organism represents its exact genetic makeup, that is,particular setgenespossesses. Two organisms whose genes differ at even one locus (positiontheir genome)saidhave different genotypes. The term "genotype" refers, then, tofull hereditary informationan organism. The phenotypean organism, onother hand, represents its actual physical properties, such as height, weight, hair color,so on.An organism's genotype islargest influencing factor indevelopmentits phenotype, but itnotonly one. Even two organismsidentical genotypes normally differtheir phenotypes. One experiences thiseveryday lifemonozygous (identical) twins. Identical twins sharesame genotype, since their genomesidentical; butnever havesame phenotype, although their phenotypes may be very similar. Thisapparent infact that their mothersclose friends can always tell them apart, even though others might not be ableseesubtle differences. Further, identical twins can be distinguished by their fingerprints, whichnever completely identical.
The conceptphenotypic plasticity describesdegreewhich an organism's phenotypedetermined by its genotype. A high levelplasticity means that environmental factors havestrong influence onparticular phenotype that develops. If therelittle plasticity,phenotypean organism can be reliably predicted from knowledge ofgenotype, regardlessenvironmental peculiarities during development. An examplehigh plasticity can be observedlarval newts1 when these larvae sensepresencepredators such as dragonflies,develop larger headstails relativetheir body sizedisplay darker pigmentation. Larvaethese traits havehigher chancesurvival when exposed topredators, but grow more slowly than other phenotypes.
In contrastphenotypic plasticity,conceptgenetic canalization addressesextentwhich an organism's phenotype allows conclusions about its genotype. A phenotypesaidbe canalized if mutations (changes ingenome) do not noticeably affectphysical properties oforganism. This means thatcanalized phenotype may form fromlarge varietydifferent genotypes,which case itnot possibleexactly predictgenotype from knowledge ofphenotype. If canalizationnot present, small changes ingenome have an immediate effect onphenotype that develops.
See also: fitness landscape
Bibliography
- J. Van BuskirkB. R. Schmidt, "Predator-induced Phenotypic PlasticityLarval Newts: Trade-offs, Selection,VariationNature," Ecology 81 (2000): 3009-3028.
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