Altered incidence of meiotic errors and Down syndrome birth under extreme low socioeconomic exposure in the Sundarban area of India.

We conducted a survey to analyze the genetic epidemiology of trisomy 21 Down syndrome births in the Sundarban delta region of India. In this region, inhabitants are chiefly from marginalized poor tribal communities and have lived in extremely low socioeconomic condition for several generations. Microsatellite genotyping revealed an meiosis I/meiosis II ratio that is different from the previous reports on the Down syndrome populations from other parts of the world. Analyses of distribution of achiasmate nondisjunction at maternal meiosis I in interaction with different maternal age groups (young, middle, and old) revealed a very concordant pattern to that of urban and semi-urban Down syndrome cases previously studied by our group. However, the frequency of achiasmate meiosis is much lower, which suggests that extreme low socioeconomic exposure imparts risk of chromosomal nondisjunction even when the maternal chromosomes 21 engage in proper chiasma formation at prophase I of oogenesis.