Young mothers and higher incidence of maternal meiosis-I non-disjunction: Interplay of environmental exposure and geneticalterations during halt phase in trisomy 21

Abstract

Trisomy 21 is a genetic condition caused when chromosomes fail to separate during meiosis. We havestudied conventional karyotype and QF-PCR using STR markers with high polymorphism and hetero-geneity and the results were analyzed, to determine the paternal and meiotic origin of trisomy 21. Thisstudy was conducted using a detailed questionnaire to include: paternal, maternal, clinical and familyhistory for various confounding factors such as age and regional environmental exposures where theparents resided. Out of 120 samples 95% (N = 114) were of maternal origin, including 92% (N = 105) ofmeiosis 1 errors and 8% (N = 9) meiosis 2 errors. Paternal origin accounted for 5% (N = 6) and were all dueto meiosis-I errors. The higher incidence of maternal meiosis-I observed in the present study suggeststhat human trisomy 21 non-disjunction is a result of multiple factors contributing to the origin of thegenetic condition.