[Non-fluorescent Y chromosome in a 45,X/46,XY mosaic (author's transl)].

The case of a 18-year-old boy with small testes and deficient growth is reported. Histological examinations revealed an abnormal structure of the testicular tissue. The X chromatin test in buccal smears and the Y chromatin test in peripheral blood lymphocytes were negative. By chromosomal studies a 45,X/46,XY mosaicism was diagnosed. The Y chromosome did not show the typical fluorescence. Autoradiographic as well as Q- and G-banding techniques were performed in both the patient and his father. The patient's Y chromosome was shorter than his father's one, but longer than the non-fluorescent part of the paternal Y. The autoradiographic grain counts, Q- and G-band patterns showed a difference between the proband's Y chromosome and that of the father. The mechanism of the observed aberration is discussed.