Unstable translocation t(14;21) in a man, inherited as a t(13;14) in one of his daughters.

The transmission of a Robertsonian translocation was studied in a family after diagnosis of a t rob. (13;14) in a foetus, in the course of a prenatal diagnosis for maternal age. The father was found to be a carrier of a balanced t rob. (14;21) in mosaicism with a normal karyotype. The t rob(14;21) was inherited from the paternal grandfather. A second prenatal diagnosis, 1 year later, revealed a girl with the paternal t rob(14;21). Mitotic and germinal instability of the paternal t rob.(14;21) is discussed, with relation to the long period of drug addiction.