CHARACTERIZATION OF A SATELLITED NONFLUORESCENT Y-CHROMOSOME (Y-NFQS)BY FISH

A fetus was prenatally diagnosed as having a Y-nfqs chromosome which w as inherited from the father. With the QFQ technique, the Yqh was obse rved to be nonfluorescent and contained cytological satellites which w ere attached to the terminal long arm. The satellites were positively stained by the Ag-NOR technique suggesting that the NORs were active. A battery of DNA probes was used to characterise the Y-nfqs. Hybridisa tion experiments using a chromosome 15 specific classical satellite DN A probe (D15Z1) and a Yq telomere DNA probe showed that the additional satellited material on Yq originated from 15p, and that the Yq termin al region had been lost. This is the first reported case in which the origin of cytological satellites on Yq has been determined by FISH, bu t this does not imply that all satellited Y chromosomes are derived fr om 15p. However, the clinical significance of this Y-nfqs chromosome r emains obscure.