Phenotype
The phenotype is the whole of the observable features (anatomical characters , morphological, molecular, physiological, ethologic) characterizing an living being given (ex: color of the eyes, the hair, Phénylcétonurie…).
The phenotype is depend on the Génotype or more precisely on the identity of the Allèle S related by each individual to one or more positions of the Chromosome S, but the influence of the medium can also be important combined with that of the Génotype.
Many phenotypes are dependant on multiple genes and influenced by certain specific conditions of the medium. However, the presence of a given allele inevitably does not make it possible to envisage the phenotype obtained.
Moreover, as the phenotypes are much easier to observe than the genotypes (no large material is necessary to know the color of the eyes of an individual), the traditional genetic uses the phenotypes to deduce the functions from genes. Experiments of crossing make it possible to study the interactions. Thus the first geneticists were able to work without any knowledge of Molecular biology.
The phenotypical variations (due to the genetic Variations) are an basic element of the evolution by Natural selection. The selective Valeur (fitness) of an organization is related to a high level phenotype determined by the contribution of thousands of more specific phenotypes. Without phenotypical variation, all the individuals would have the same selective value and the phenotypical changes would not be done without any selection (randomly).
The interaction between genotype and phenotype is often conceptualized by this type of relation: genotype + environment + random variation → phenotype
Certain species as the common Truite can develop very different phenotypes starting from the same genotype according to the medium: in this case typically growth in river, in lake or at sea.
Various levels of definition of the phenotype
- on the level of the organization: macroscopic Phenotype
- on the level of the cells: cellular Phenotype
- on the level of the molecules: molecular Phenotype
See too
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