“…The translocation most frequently reported involves the attachment of chromosome number 21 to a chromosome in the 13-14-15 group (so-called 15/21 translocation) while in other instances combinations of 22/21 and 21/ 21 have been observed in translocation mongolism (Atkins, O'Sullivan, & Pryles, 1962;Biesele, Schmid, Lee, & Smith, 1962;Book, Santesson, & Zetterqvist, 1961;Carter & Evans, 1961;Carter, Hamerton, Polani, Gunalp, & Weller, 1960;Ek, Falk, Bergman, & Reitalu, 1961;Fraccaro, Kaijser, & Lindsten, 1960;Hamerton, Cowie, Giannelli, Briggs, & Polani, 1961;Hamerton & Steinberg, 1962;Lehmann & Forssman, 1962;Macintyre, Staples, Steinberg, & Hemple, 1962;Penrose, Ellis, & Delhanty, 1960;Polani, Briggs, Ford, Clarke, & Berg, 1960;Scherz, 1962;Shaw, 1962;Turpin & Lejeune, 1961;Turpin, Lejeune, Lafourcade, & Gautier, 1959). Various families have been described in which Down's syndrome, due to translocation of chromosome number 21, has affected several members of succeeding generations.…”