Text Box: RAPID PRENATAL GENE DIAGNOSIS IN TRISOMY 21 SYNDROME BY IN SITU HYBRIDIZITION Zhou Dongfeng, Meng Pu Department of Pediatrics, Union Hospital of Tongji Medical College, Huazhong Science and Technology University, Wuhan, China Objective: To explore a rapid, simple diagnosis method and prenatal diagnosis method in trisomy 21 syndrome. Methods: Using human chromosome 21 specific probe, in situ Hybridization was carried out in peripheral blood. Cells of trisomy 21 individuals, in villi cells or amniotic fluid cells of artificial abortion donors and prenatal diagnostic individuals. All the samples underwent chromosome analysis in the same time. Results: Under the microscope the majority (75-86%) of trisomy 21 individuals exhibited 3 discrete spots。In contrast, the normal villa cells and prenatal diagnostic individual nuclei showed 2 foci usually. After birth, the karyotape in the case of prenatal diagnosis accorded with the results of in situ hybridization. Conclusion: This technique can be used to diagnose and prenatal diagnose because it is simple, rapid and high specific. 2379