CHARACTERIZATION OF AN UNBALANCED DE-NOVO REARRANGEMENT BY MICROSATELLITE POLYMORPHISM TYPING AND BY FLUORESCENT IN-SITU HYBRIDIZATION

Unbalanced de novo rearrangements, difficult to characterize by conven tional cytogenetic techniques, may be elucidated by molecular approach es, By dinucleotide repeat polymorphism typing and fluorescence in sit u hybridization (FISH), we have defined the composition of an unbalanc ed de novo translocation (46,XX,15p+) in a child with multiple congeni tal anomalies, Use of a microsatellite repeat D5S208 (localized to 5p1 5) and polymerase chain reaction (PCR) analysis confirmed that the ext ra segment originated from the short arm of chromosome 5. Amplificatio n of the patient's DNA with primers for dinucleotide repeats D5S350 an d D5S118 showed that the entire 5p (from 5pter to 5q11) was present in 3 copies, FISH confirmed the trisomic status of 5p, and further revea led the presence of centromeres of both chromosomes 5 and 15 on the re arranged chromosome thus delineating its dicentric nature, This inform ation allowed us to redefine the de novo rearrangement in this patient as 46,XX,dic der(15)t(5;15)(q11;p11). (C) 1995 Wiiey-Liss, Inc.