Dissociation as probable origin of mosaic 45,XY,t(15;21)/46,XY,i(21q).

Abstract
A patient is described with some features of Down''s syndrome and a 45,XY,t(15;21)(15qter .fwdarw. 15p13::21p11 .fwdarw. 21qter)/46,XY,i(21)(qter .fwdarw. cen .fwdarw. qter) karyotype. Two mechanisms are proposed for the origin of the mosaicism, 1 assuming the dissociation of a translocation (15;21) chromosome already present in the zygote, and the other involving a chromatid translocation in a 46,XY zygote. The possible independent origin of the 2 cell lines is considered.