Question

If the gene is non-penetrant then which of the following is not right?

(a) The pedigree chart will not express the defecting phenotype in that individual

(b) The person’s children are not likely to express that phenotype

(c) The expressivity is 0%

(d) The genotype here didn’t make its proper phenotypic expression

I have been asked this question in quiz.

My question comes from Penetrance and Expressivity in section Regulating Gene Expression in Eukaryotes of Cytogenetics

Answer 1

Right option is (b) The person’s children are not likely to express that phenotype

To explain: If the gene is non-penetrant for an individual it is not mandatory that it will also be non-penetrant for his offspring. As a result, the pedigree could appear to skip a generation with the parent being a carrier.