Morphological detection of X- and Y-chromosomes in smears and paraffin-embedded tissues using a non-isotopic in situ hybridization technique (NISH).

Pharyngeal smears and paraffin-embedded tissue specimens (skeletal muscle, kidney) obtained from 10 male and 10 female individuals were evaluated using non-isotopic in situ hybridization (NISH) with commercial X- and Y-specific biotinylated probes which recognize the pericentromeric regions DXZ1 and DYZ1/DYZ3 of the X- and Y-chromosome, respectively. The results provide evidence that the morphological sex determination of a single cell can be performed by critical application of this staining method leading to one nuclear signal in "male" cells using the Y-specific probe whereas "female" cells are negative. In situ hybridization of "female" tissues with an X-specific probe results regularly in 2 signals whereas "male" cells show only one spot in the nucleus.