Incomplete penetrance
From SNPedia
Carriers of a harmful gene variant or SNP, even one that is considered a dominant mutation, may not develop the associated disease. This type of mutation is said to have reduced or incomplete penetrance[1] Retinitis pigmentosa is an example of an inherited condition that may appear to "skip generations" because of reduced penetrance.[PMID 18640990]
Many additional terms are defined in the SNPedia Glossary page, including penetrance.
