Phenotype

Phenotype refers to the observable physical properties of an organism; these include the organism's appearance, development, and behavior. An organism's phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes. The interaction between genes and environment that produces the phenotype is often referred to as the norm of reaction.

Definition and usage

The term phenotype has been derived from the Greek words phainein (meaning "to show") and typos (meaning "type"). It was first used by Wilhelm Johannsen in 1911. Phenotype encompasses all of the observable characteristics of an organism, resulting from the interaction of its genotype with the environment.

Relationship with genotype

The genotype of an organism is the inherited instructions it carries within its genetic code. Not all organisms with the same genotype look or act the same way because appearance and behavior are modified by environmental and developmental conditions. Likewise, not all organisms that look alike necessarily have the same genotype.

Phenotypic variation

Phenotypic variation (due to underlying heritable genetic variation) is a fundamental prerequisite for evolution by natural selection. It is the living organism as a whole that contributes (or not) to the next generation, so natural selection affects the genetic structure of a population indirectly via the contribution of phenotypes. Without phenotypic variation, there would be no evolution by natural selection.

See also

• Genotype
• Genetics
• Evolution
• Natural selection

References

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