The phenotype of an individual organism is either its total physical appearance and constitution, or a specific manifestation of a trait, such as size or eye color, that varies between individuals. Phenotype is determined to some extent by genotype, or by the identity of the alleles that an individual carries at one or more positions on the chromosomes. Many phenotypes are determined by multiple genes and influenced by environmental factors. Thus, the identity of one or a few known alleles does not always enable prediction of the phenotype. In biology and ecology, an organism (in Greek organon = instrument) is an assembly of molecules that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... In biology, a trait or character is a genetically inherited feature of an organism. ... The genotype is the specific genetic makeup (the specific genome) of an individual, usually in the form of DNA. It codes for the phenotype of that individual. ... An allele is any one of a number of alternative forms of the same gene occupying a given locus (position) on a chromosome. ... Figure 1: Chromosome. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... An environment is a complex of external factors that acts on a system and determines its course and form of existence. ...

Nevertheless, because phenotypes are much easier to observe than genotypes (it doesn't take chemistry or sequencing to determine a person's eye color), classical genetics uses phenotypes to deduce the functions of genes. Breeding experiments can then check these inferences. In this way, early geneticists were able to trace inheritance patterns without any knowledge whatsoever of molecular biology. In genetics and biochemistry, sequencing means to determine the primary structure (or primary sequence) of an unbranched biopolymer. ... Classical genetics consists of the techniques and methodologies of genetics that predate the advent of molecular biology. ... Molecular biology is the study of biology at a molecular level. ...

The interaction between genotype and phenotype has often been described using a simple equation:

genotype + environment → phenotype

A phenotype is any detectable characteristic of an organism (i.e. structural, biochemical, physiological and behavioral) determined by an interaction between its genotype and environment (see genotype-phenotype distinction and phenotypic plasticity for a further elaboration of this distinction). In biology and ecology, an organism (in Greek organon = instrument) is an assembly of molecules that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... The genotype is the specific genetic makeup (the specific genome) of an individual, usually in the form of DNA. It codes for the phenotype of that individual. ... The genotype-phenotype distinction refers to the fact that while genotype and phenotype of an organism are related, they do not necessarily coincide. ...

The idea of the phenotype has been generalized by Richard Dawkins to include effects on other organisms or the environment in The Extended Phenotype. Dawkins is the holder of the Charles Simonyi Chair in the Public Understanding of Science at the University of Oxford. ... The Extended Phenotype is a 1982 book by biologist Richard Dawkins and is sometimes a reference to the idea expounded in that book. ...

See also

• Genetics
• Trait