TRISOMIC ZYGOTE RESCUE REVEALED BY DNA POLYMORPHISM ANALYSIS IN CONFINED PLACENTAL MOSAICISM

Uniparental disomy can be caused by different genetic mechanisms such as gamete complementation, chromosome duplication in monosomic zygote, or post-zygotic aneuploidy correction. This last mechanism is well do cumented in human reproduction and is related to placental mosaicism. In the case of a trisomic zygote which has originated by paternal or m aternal non-disjunction at the first or second meiotic cell division, mosaicism will result from chromosome loss and restoration of a 'norma lized' diploid fetal karyotype. In order to enrich the literature with new observations on this subject, we studied by DNA polymorphism anal ysis ten cases of confined placental mosaicism (CPM). The finding in p lacental DNA of three different alleles at polymorphic loci of chromos omes 13, 16, and 20 demonstrated the trisomic status of the zygote in three cases. On the basis of these results, we believe that systematic DNA polymorphism analysis could give useful additional information to improve knowledge on aneuploidy correction in human reproduction. (C) 1998 John Wiley & Sons, Ltd.