expressivity

Full Definition

Expressivity refers to the variation in severity, extent, or specific features of a genetic condition among individuals who carry the same disease-causing variant. While penetrance determines whether a condition manifests at all, expressivity describes how it manifests when it does occur. Variable expressivity means that family members with the same genetic change may have different symptoms or severity levels, which has important implications for genetic counseling and family planning decisions.

Usage

Usage note: Often qualified as 'variable expressivity' in clinical contexts.

In Context

• "The family demonstrated variable expressivity, with symptoms ranging from mild learning difficulties to severe intellectual disability." — Clinical genetics report
• "Variable expressivity complicates predictions about how severely an unborn child might be affected." — Genetic counseling documentation