A DE-NOVO SATELLITED SHORT ARM OF THE Y-CHROMOSOME POSSIBLY RESULTINGFROM AN UNSTABLE TRANSLOCATION

A satellited long arm of the Y chromosome (Yqs) is considered a normal variation, whereas the presence of a satellite on the short arm of th e Y (Yps) has never been described in the literature. A Yps chromosome could be clinically significant if the translocation resulting in Yps has relocated the testis-determining gene, SRY, to another chromosome . A carrier of such a translocation would therefore be at increased ri sk for having XX male and XY female offspring. Here we describe the fi rst reported case of de novo Yps present in a phenotypically normal ma le. This Yps chromosome was positive for C-banding and nucleolus organ izer region (NOR) staining and showed a hybridization signal for the b eta-satellite sequence. Fluorescence in situ hybridization (FISH) anal ysis indicated that SRY was retained on the Yps and the translocation breakpoint on Yps was distal to the pseudoautosomal region. At prenata l diagnosis, a normal appearing Y chromosome was found in his son, and thus the satellite on Yps was lost during meiotic Xp-Yp pairing. This Yps chromosome was likely the product of an ''unstable'' translocatio n.