RAPID DETECTION OF DOWN SYNDROME BY SHORT TANDEM REPEAT ANALYSIS FROM EASTERN INDIA

Abstract

Down syndrome (DS) is the most common chromosomal disorder in human, caused by an extra copy of chromosome 21(Ward et al. 1999). It constitutes the most frequent form of intellectual disability. The cytogenetic prole of down syndrome includes trisomy 21, Robertsonian translocations, mosaicism, duplication of the critical region and other structural rearrangement involving chromosome 21(Verma et al. 1998,). India has the highest number of people suffering from DS in the world (Sherman et al 2007). The high prevalence is mainly due to lower level of care considered for 2/3 of Down syndrome pregnancies that are under 35 years of mother age and low level of information behind etiology of Down syndrome for instance about advanced maternal age(Van Montfrans et al. 2002). To reduce signicantly the birth prevalence of Down syndrome, a wide-ranging screening of pregnant women has been suggested (Pertl et al. 1996). However, conventional methods such as cytogenetic analysis for diagnosis of chromosomal abnormalities often need lengthy laboratory procedures, and expertise, are expensive as well as signicant delay in obtaining a diagnosis (Patterson et al. 2005). Applying of uorescence in situ hybridization technique from late 1980s using uorescently labeled DNA probe has facilitated analysis of chromosome abnormalities. However, genotyping of short tandem repeats (STR) on chromosome 21 is an alternative rapid inexpensive & reliable method for the identication of DS child and is also even suitable for large scale screening of pregnant women (Rahil et al. 2002). The STRs are the hypervariable regions of the genome with variable repeat length and can be used for the quantitative analysis of extra chromosome of 21. This study aims to identify the DS child using simple PCR based analysis of STR markers on chromosome 21 among the eastern Indian population.