Nondisjunction in Trisomy 21: Origin and Mechanisms

Abstract

Down’s Syndrome is a chromosomal abnormality with a gain of a third copy of chromosome 21, characterized by craniofacial abnormalities, intellectual developmental delay and growth retardation. In the present study, one-day-old neonate and a patient with an aborted fetus were presented to rule out genetic aberrations via CMA screening. DNA was extracted using from the case samples and evaluated by CMA Affymetrix platform. Chromosomal abnormalities in the fetus such as trisomy emerges due to several factors including maternal age, genetic mutational events, non-disjunction of chromosomes and epigenetic changes. Genetic Cause of trisomy 21 is chromosomal aneuploidy and gain of three copies of chromosome 21. The Trisomy 21 can occur due to Robertsonian translocation, Mosaicisms or duplication of critical region of chromosome 21. The trisomy 21 is the result of nondisjunction of homologous chromosomes 21 during gametogenesis at the time of embryo development. CMA is an effective molecular diagnostic tool for predicting and diagnosing chromosomal abnormalities which needs to be promoted in India for healthy pregnancy outcomes. We report two cases of confirmed post-natal Trisomy 21. The main aim of this study is to focus on genetic diagnosis and its awareness which is still lacking with 100% coverage, in developing countries to reduce the burden of genetic diseases and associated emotional and economic consequences.