Background. DNAsequences from chromosomeYcan cause gonadoblastoma development in patientswith Turner syndrome (TS). Estimated risk is about 30%. The aim of the study is detection of Y-sequences on DNA level, calculation of mosaicism and its cytogenetic location. Clinical result of the study is the recommendation to gonadectomy of proved positive patients. Methods and Results. Samples from 110 patients were collected. The PCR method and analysis of products on agarose gel was compared with analysis of DNA fragments from quantitative fluorescent (QF) PCR on capillary electrophoresis. The loci DYZ3, AMGX/Y and SRY were used for detection. The method QF PCR was effected for DYZ3 and AMGX/Y loci. The positive cases were examined by FISH method. Five (4,5 %) and 3 (2,7 %) positive cases were detected in DYZ3 and SRY resp. loci by electrophoresis on agarose gel. Seventeen (15,5 %) and 7 (6,4 %) positive cases were detected in DYZ3 and AMGX/Y resp. by capillary electrophoresis. The estimated mosaicism ranged from 1:5 to 1:100 000. Conclusions. QG PCR is the most sensitive method for diagnostics of Y-sequences. Simultaneously the incidency of Y-positive cells can be estimated. The positive cases with marker in karyotype were confirmed by FISH.

        Key words: Turner syndrome, Y chromosome, gonadoblastoma, capillary electrophoresis.