RESUMO
Objective Setting a rapid, simple and accurate gene diagnosis method for trisomy 21 syndrome. Methods 4 short tandem repearts (STRs) loci (D21S11, D21S1411, D21S1412, D21S1414) in and near the core region(21q22.1-21q22.2) on 21 chromosome of blooding samples from 8 normal people, 11 cases of trisomy 21 syndrome and 1 case of fetus umbilical core were analyzed and detected by polymerase chain reaction(PCR), polyacrylamide gel electrophories, and silver staining. Results 6/8? 7/8? 3/8?7/8 of normal people showed two bands with a DNA content ratio of 1∶1. 2/8?1/8?5/8?1/8 of normal people showed one band in 4 loci. 7/11?8/11?6/11?7/11 of all patients showed two bands with a DNA content ratio of 2∶1;3/11?2/11?2/11?3/11 showed three bands with a DNA content ratio of 1∶1∶1. 1/11?1/11?3/11?1/11 showed one band. The blooding sample of fetus showed two bands with a DNA content ratio of 2∶1 at 3 loci and one band at 1 locus. 11 patents and 1 fetus were identified as trisomy 21 syndrome by analysis combining with 4 STR loci. Conclusion The 4 selected STR loci have high polymorphism.4 polymorphotic STR is a valuable gene marker for diagnosis of trisomy 21. Trisomy 21 can be diagnosed rapidly and accurately within 24 hours by PCR.