What is the degree to which a genotype is expressed in phenotype known as?

The degree to which a genotype is expressed in phenotype is known as expressivity. This term refers to the varying degrees to which a particular genotype manifests as a phenotype among individuals exhibiting the same genotype. In essence, expressivity can highlight the differences in physical traits, symptoms, or characteristics that can occur even among individuals with identical genetic makeups.

For instance, if a gene is responsible for a trait like a certain eye color, expressivity would describe how intensely that trait is displayed among different individuals—some may exhibit a lighter shade while others display a deeper hue. This variation can be influenced by several factors, including environmental influences, interactions with other genes, and individual developmental differences.

In contrast, penetrance refers to the proportion of individuals with a specific genotype that actually express that phenotype, indicating whether a trait will manifest at all rather than its degree of expression. The term phenotypic ratio describes the relative number of offspring with specific traits from genetic crosses but does not pertain to the expressivity of a single genotype. Lastly, "genetic expressiveness" is not a recognized term in the field of genetics. Thus, expressivity is the most accurate term for describing the extent of phenotype expression related to a genotype.