Medical Definition of Nonpenetrant trait
Nonpenetrant trait: A genetic trait (characteristic) that is present in the genome but does not manifest itself in the individual. By contrast, a penetrant trait is one that manifests itself.
If, for example, if 100 people have a particular genetic trait but only 80 of them express it, the penetrance of that trait is 80%. The trait is nonpenetrant in 20% of people who have it.
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