【Abstract】 Objective: This study was designed to explore the diagnosis on Down syndrome by fluorescence in situ hybridization (FISH). Methods: We detected trisomy 21 with Down syndrome cristical region cosmid DNA probe, which comes from specific KU21D library of chromosome 21 (carrier is 6.7 kb, insert sequence is 35 kb) and is located in 21q22.2. 48 cases of trisomy 21 were detected on cultured and uncultured lymphoblastoid cell by FISH. Results: There were three hybridization points in interphase nuclei and three hybridization signals on metaphase three chromosome 21. Hybridization rate was 81%～95%. Conclusion: Trisomy 21 could be diagnosed rapidly and accurately by DSCR Cosmid DNA probe in uncultured lymphoblastoid interphase unclei of patients.更多还原