penetrance
The proportion of individuals with a specific genetic variant who actually express the associated phenotype or clinical features.
Full Definition
Penetrance is a fundamental genetic concept describing the likelihood that an individual carrying a disease-causing genetic variant will actually develop the associated condition. Complete penetrance (100%) means everyone with the variant develops the condition, while reduced or incomplete penetrance means only some carriers are affected. This concept is crucial in reproductive genetics for counseling families about inheritance risks and interpreting genetic test results, as some conditions show age-dependent or variable penetrance patterns.
Usage
Usage note: Often expressed as a percentage when discussing specific conditions.
In Context
- "The BRCA1 mutation shows 80% penetrance for breast cancer by age 70." — Genetic counseling session
- "Due to reduced penetrance, not all family members carrying the variant will develop symptoms." — Patient information leaflet