The phenotype ( ancient Greek φαίνω phaíno "I appear" and τύπος týpos "shape") or the appearance is the set of all characteristics of an organism in genetics . It refers not only to morphological , but also to physiological properties and, if necessary, to behavioral characteristics .
The phenotype is determined by the interaction of genetic makeup and environmental factors ( modification ). The extent to which the phenotype can be influenced by environmental influences depends on the reaction norm. This possibility of reacting to environmental influences is genetically determined by the genotype . Process with which conclusions from the genetic material , d. H. of the individual deoxyribonucleic acid (DNA), inferring the phenotype of an individual, is called DNA phenotyping .
If environmental influences can cause a high variability in the appearance of an individual, one speaks of high phenotypic plasticity or a large range of variation or modifiability. However, if the phenotype is largely predetermined by its genotype , this indicates poor plasticity. The concept of phenotypic plasticity describes the extent to which the phenotype of an organism is predetermined by its genotype. A high value for plasticity means: environmental influences have a strong influence on the individually developing phenotype. If plasticity is low, the phenotype can be reliably predicted from the genotype, regardless of special environmental conditions during development. High plasticity can be observed in the example of the larvae of two newt species: When these larvae perceive the presence of predators such as dragonfly larvae, the head and tail enlarge in relation to the body, and the skin is pigmented darker. Larvae with these traits have better chances of survival than predators, but grow more slowly than other phenotypes. Phenotypic changes due to environmental influences are called modifications. For example, genetically identical plants (e.g. cuttings) can develop completely different growth forms at different locations.
If an exogenous (not hereditary) factor encounters an organism in a certain period of development, a characteristic can be developed in the same way as in the case of a genetic change (mutation). In this case one speaks of phenocopy.
In the biomedical field, almost always in connection with animal models in animal experiments , the model of the phenotype is occasionally expanded to include the "drama type". The term was introduced in 1959 by WMS Russell and RL Burch. This represents the, mainly physiological , reaction to the immediate, current environment, while the development of the phenotype relates to a longer period of time. Knowing the type of drama makes it possible to better standardize the test conditions and thus improve the reproducibility of the results.
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- German Mouse Clinic - facility for phenotyping of mice (English)
- The Human Phenotype Ontology - vocabulary for describing human phenotypes
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