محبوبه نصیری
مرتضی جبارپور بنیادی
محمد امین بخش
امید عمرانی
فضیله هاشمی
محمد حیدزاده

Background & Objective: Down syndrome is one of the most common chromosome aneuploidies causing mental retardation which occurs in approximately ۱/۲۳۰ pregnancies. It is usually caused by the presence of an extra chromosome ۲۱. The aim of this study was to evaluate the simple PCR based DNA diagnostic method and also to determine the parental origin of the extra chromosome ۲۱ in trisomal Down syndrome. Materials & methods: To determine the polymorphism rates of chromosome ۲۱ microsatellite markers, ۵۰ people from Eastern Azarbayjan were randomly selected and studied for the microsatellites. The results were statistically analyzed. Thirty affected Down syndrome patients, diagnosed by specialists were referred to the lab for further molecular analysis. After genetic counseling and getting consent, blood samples were obtained. Seven pairs of chromosome ۲۱ microsatellite markers were amplified using PCR in all the samples. Results: Five highly polymorphic microsatellite markers were selected from a total seven markers, studied in ۵۰ normal people. Out of ۳۰ Down syndrome’s patients, trisomal ۲۱ was diagnosed in ۲۱ families (۷۰%). In which non-disjunction errors were determined to be of maternal origin in ۸۶% and of paternal origin in ۹% of the cases. The mean maternal and parental age was ۳۳/۳ and ۳۶/۲, respectively. Conclusion: The three microsatellite markers, D۲۱S۱۹۱۰, D۲۱S۱۴۱۱ & D۲۱S۱۱ could diagnose a high percentage of trisomal ۲۱ in Down syndrome’ patients. The parental origin of an extra copy of chromosome ۲۱ could be exactly determined.

Down Syndrome, Microsatellite Markers, East-Azarbayjan Population, Parental Origin of Chromosome