IDENTIFICATION OF THE PARENTAL ORIGIN OF POLYSOMY IN 2 49,XXXXY CASES

The parental origin and mechanism of formation of polysomy X were stud ied in two polysomic cases, using four X-linked restriction fragment l ength polymorphisms, three (CA), dinucleotide repeat sequences and one variable number tandem repeat (VNTR) locus as genetic markers. A nonr adioactive technique based on the hybridization of the polymerase chai n reaction (PCR) product was developed for the analysis of dinucleotid e repeats. Segregation analysis using different nonradioactive approac hes based on the PCR, revealed that all four X chromosomes were of mat ernal origin. These data provide additional evidence of an identical m echanism of successive nondisjunctions in maternal meiosis I and II.