A form of penetrance in which not all individuals carrying a deleterious gene express the associated trait or condition.
A disease is said to show incomplete penetrance when some individuals express the associated trait while others do not even though they carry the disease-causing gene. For instance, some people with a mutation in the BRCA1 or BRCA2 gene will develop cancer during their lifetime, other people will not.
‘’Synonym:’’ reduced penetrance
Compare: complete penetrance