Incomplete penetrance

In a life time penetrance, Is the phenotype expressed at an unpredictable time during a person’s life?
And when it’s stated that a particular disease has a thirty year penetrance, does it mean that the diseases will be expressed in the first 30 years of an individual?

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Hi! So I found out the penetrance of a genetic disorder is measured by evaluating how OFTEN a particular phenotype occurs given a particular genotype or vice versa. So different people who have the gene or the genotype for the particular trait, there is a variation in how it is expressed in the phenotype. Some people may show a few symptoms or others all. The penetrance is sort of the measure of the frequency of the appearance of the phenotype.

Certain factors are known to influence the gene penetrance for specific disorders. For example, phenotypic expression of a particular phenotype may be modified by age, termed age-related penetrance. Sometimes, as age increases, penetrance increases. So I think in your case, it could be that after 30 years, the penetrance reduces so the expression of the phenotype changes. It could also be gender related!

I found an example of an autosomal dominant disorder which could be misinterpreted because the parents have reduced penetrance at their age so it’s not expressed while their children are affected.

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