The project was proposed to study the parental and meiotic origin of trisomy 21 by conventional karyotyping alongwith QF-PCR (Quantitative fluorescent polymerase chain reaction) and STR Markers. 122 DS patients from Gujarat (Western India) were enrolled in the study with their parents following informed consent. The Medical Genetics department of SGPGI Lucknow provided facility and expertise for QF-PCR studies. The result showed 95% of aneuploidy is of maternal origin and out of which 92% of the non-disjunction occurs due to the maternal meiotic error I (MMI). Our observation also suggests that there is no apparent relation between meiotic errors and the maternal age distribution.