phénotype

Phénotype, or phenotype, is the set of observable characteristics of an organism that result from the interaction of its genotype with the environment. It includes physical form, physiological function, behavioral traits, and biochemical properties. The term contrasts with genotype, the organism's genetic makeup, which provides the blueprint but does not by itself determine all outcomes. Phenotypes arise through gene expression during development and can be influenced by nutrition, climate, stress, and other environmental factors.

Phenotypes can be simple or complex. Simple (Mendelian) traits may be determined by a single gene with dominant and recessive alleles, such as certain coat colors in animals. Most traits, however, are polygenic, determined by many genes, often with small effects, such as height or metabolic rate, and are strongly shaped by the environment. Phenotypic plasticity refers to the ability of a single genotype to produce different phenotypes under different conditions. Epigenetic changes can also modify gene expression and influence phenotype without altering the DNA sequence.

The study of phénotype includes morphology, physiology, behavior, and disease manifestations. In medicine and biology, phenotypic information complements genotypic data for diagnosis, treatment, and understanding evolution and development. Measurements of penetrance (the proportion of individuals with a genotype who exhibit the phenotype) and expressivity (the degree to which a phenotype is expressed) help describe variability among individuals.