Fænotypen

Fænotypen, commonly referred to as the phenotype, denotes the observable traits of an organism. These traits include external appearance such as height or leaf shape, as well as internal characteristics like metabolism, physiological processes, and behavior. The phenotype results from the interaction between the organism’s genotype and its environment, and can change with age or developmental stage.

The relationship between genotype and phenotype is not one-to-one. Traits can be simple, controlled by a single gene, or complex, influenced by many genes and their interactions with environmental factors. Phenotypes are affected by gene expression, developmental timing, nutrition, climate, and other conditions. Concepts such as penetrance (how often a genotype manifests) and expressivity (the degree of manifestation) describe variability in phenotypic outcomes.

Historically, the term reflects the observable “appearance” of an organism and contrasts with the underlying genetic code. The word has roots in Greek, with phainō to appear and typos meaning model or type, and was formalized in genetics in the early 20th century.

Examples of phenotypes range from obvious traits like flower color and body size to more complex features such as metabolic profiles or behavioral tendencies. In medicine, phenotype assessment aids diagnosis, prognosis, and monitoring of disease; in agriculture, phenotyping supports breeding by linking observable traits to desirable performance.

Modern research emphasizes genotype–phenotype mapping, recognizing the roles of epigenetics, gene–environment interactions, and plasticity. While genomics provides data on potential traits, the realized phenotype reflects both inherited information and environmental context.