page_title: Phenotype
section_title: Difficulties in definition
hierarchical_section_title: Phenotype / Difficulties in definition
caption_attribution_description: English: How to determine the blood group based on the blood type alleles.
context_page_description: Phenotype is the term used in genetics for the composite observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological properties, its behavior, and the products of behavior. An organism's phenotype results from two basic factors: the expression of an organism's genetic code, or its genotype, and the influence of environmental factors. Both factors may interact, further affecting phenotype. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented example of polymorphism is Labrador Retriever coloring; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black, and brown. Richard Dawkins in 1978 and then again in his 1982 book The Extended Phenotype suggested that one can regard bird nests and other built structures such as caddis-fly larvae cases and beaver dams as "extended phenotypes".
context_section_description: Despite its seemingly straightforward definition, the concept of the phenotype has hidden subtleties. It may seem that anything dependent on the genotype is a phenotype, including molecules such as RNA and proteins. Most molecules and structures coded by the genetic material are not visible in the appearance of an organism, yet they are observable (for example by Western blotting) and are thus part of the phenotype; human blood groups are an example. It may seem that this goes beyond the original intentions of the concept with its focus on the (living) organism in itself. Either way, the term phenotype includes inherent traits or characteristics that are observable or traits that can be made visible by some technical procedure. A notable extension to this idea is the presence of "organic molecules" or metabolites that are generated by organisms from chemical reactions of enzymes.
  The term "phenotype" has sometimes been incorrectly used as a shorthand for phenotypic difference from wild type, yielding the statement that a 
  "mutation has no phenotype".
  Another extension adds behavior to the phenotype, since behaviors are observable characteristics. Behavioral phenotypes include cognitive, personality, and behavioral patterns. Some behavioral phenotypes may characterize psychiatric disorders or syndromes.
caption: ABO blood groups determined through a Punnett square and displaying phenotypes and genotypes
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