Germline mosaicism

Germline mosaicism, also known as gonadal mosaicism, is a condition in which the precursor (germline) cells to ova and spermatazoa are a mixture (mosaic) of two or more genetically different cell lines.

A study of semen samples from 100 men found low-level germline mosaicism in one third of infertile men, with increased incidence with advancing paternal age.