Y chromosome--specific DNA sequences in Turner-syndrome mosaicism.

Phenotypic females with Y-chromosomal material in their genome have an increased risk for development of gonadal malignancy. The detection and identification of Y-chromosomal material in these cases can be of critical importance for medical management. Chromosome analysis in four patients with Turner syndrome revealed the characteristic 45,X chromosome complement together with a second cell population containing a small marker chromosome (46,X, + mar). Molecular-hybridization analyses utilizing cloned, Y chromosome-specific DNA sequences were performed to determine whether Y-chromosomal material was present in each patient. Three cases contained some Y chromosome-specific sequences, whereas one case was negative with all four probes that we used. These results were compared with detailed cytogenetic studies--including G-, Q-, and G-11-banding--of the marker chromosomes. In one case in which Y chromosome-specific DNA sequences were demonstrated, the marker chromosome was G-11 negative. These results demonstrate that cytogenetic analysis alone can lead to misidentification of some Y chromosome-derived markers. The combination of cytogenetic and molecular analyses permits a more accurate characterization of anomalous Y chromosomes and in turn provides additional information that can be crucial to the correct medical management of Turner-syndrome patients.