Phenotypic outcome of a genotype—key definitions The degree to which a given genotype is manifested in the phenotype of an individual is termed what?

Introduction / Context:
Two related terms—penetrance and expressivity—describe different aspects of how genotypes translate into phenotypes. Misunderstanding these terms leads to errors in interpreting pedigrees and risk assessments.

Given Data / Assumptions:

• We focus on the extent or degree of trait expression in an individual who carries the genotype.
• We are not being asked what fraction of carriers show the trait.

Concept / Approach:
Expressivity measures the severity or range of phenotypic expression among individuals with the same genotype (e.g., mild to severe). Penetrance measures the proportion of individuals with the genotype who actually show any phenotype at all (all-or-none at the individual level). Therefore, “degree or extent” points to expressivity.

Step-by-Step Solution:

Verification / Alternative check:
Clinical genetics routinely documents variable expressivity (e.g., neurofibromatosis) where all carriers may show signs, but severity varies widely.

Why Other Options Are Wrong:

• Penetrance: fraction expressing the trait, not the degree of expression.
• Inheritance strength/environmental influence/additive variance: broader concepts, not the specific definition asked.

Common Pitfalls:
Using “penetrance” whenever variation is mentioned; remember penetrance is yes/no, expressivity is how much.

Final Answer:
Expressivity