Giemsa-11 technique elucidating three structurally altered nonfluorescent Y chromosomes: r (Y), idic (Yp), dir tan dup (Yp).

Three patients are presented in whom a structurally altered Y chromosome was finally diagnosed using Giemsa-11 technique. The first patient, a 19-year-old woman with primary amenorrhea and some features of Turner syndrome had ring (Y). The second patient, a 2-year-old boy with small stature and incomplete masculinization was found to have an isodicentric (Yp). In the third patient who was examined because of ambigous genitalia the chromosome abnormality, a nonfluorescent pseudodicentric (Y) was interpreted as a direct tandem duplication of the short arm, centromere, and a piece of the long arm, a rearrangement not described before. In each of the patients Q-, G-, and C-bandings failed to elucidate the kind of chromosome abnormality. Since clarification of a given Y structural rearrangement by cytogenetic methods cannot be avoided even in the era of molecular genetics, Giemsa-11 technique should be applied in the analysis of every dubious small sex chromosome.