phenotype

The phenotype of an organism includes its observable traits—morphology, development, physiology, biochemistry, and behavior—emerging from the interaction of its genotype with the environment. It is the manifestation that results from gene expression and developmental processes, not the genetic code itself. The genotype refers to the organism's set of genes.

Traits can be categorized as morphological (height, leaf shape), physiological (metabolic rate, enzyme activity), biochemical (protein levels), or behavioral (mating calls). Some traits follow simple Mendelian inheritance, but most are quantitative and influenced by many genes and environmental factors.

The phenotype reflects gene expression, regulatory networks, and environmental inputs. Gene–environment interactions and epigenetic modifications can alter phenotypes without changing DNA sequence. Phenotypic plasticity enables different phenotypes to arise under different conditions.

Phenotyping, or phenomics, is the measurement of phenotypes across scales, from molecular assays to whole-organism traits. High-throughput approaches and standardized scoring support mapping between genotype and phenotype and help estimate heritability and genetic architecture.

In evolution, natural selection acts on phenotypes, shaping fitness and, over generations, allele frequencies. Variation in phenotype, coupled with environmental change, drives adaptation. In medicine and biology, phenotype informs diagnosis, prognosis, and personalized treatment, often alongside genomic information.

Etymology and scope: the term derives from Greek phainein to show and typos type. Today it encompasses the full set of observable characteristics, with genomics expanding the concept to connect genotype to the visible output of biological systems.