Understanding Incomplete Penetrance: Causes and Factors

Incomplete Penetrance in Genetics

Incomplete penetrance: a genotype does not always express the expected phenotype. Causes:

• Environmental factors: Gene expression may require specific conditions (temperature, light).
• Epigenetic modifications: DNA structure changes (not sequence) affecting expression; can be inherited.
• Genetic modifiers: Other genes influencing expression level or timing.
• Gene dosage: Number of gene copies; insufficient dosage may prevent phenotype expression.

Complicates genetic prediction and trait studies.