Rapid Detection Of Trisomy 21 Syndrome Use Str-pcr

BackgroundTrisomy 21 syndrome is also called Down syndrome,it is the most common chromosomal disease.As there is no effective treatment for Down syndrome now, Down syndrome children are heavy burden to the social and the family.Because the exact etiology and pathogenesis is not yet clear,there is no pre-pregnancy intervention, only through prenatal diagnosis and therapeutic abortion to prevent the born of Down syndrome.The diagnosis of the born children with Down syndrome mainly relies on peripheral blood karyotype analysis.However,the technology has a long life cycle, and the operation is cumbersome.Prenatal diagnosis of Down syndrome has been performed by chorionic villi sampling,amniocentesis and cordocentesis,but disadvantages of these methods include high cost,difficulties in cell culture,and significant time requirements.The fluorescence in situ hybridization(FISH) is a new fast technology developed in recent years,and it is a good supplement to amniotic puncture.However,it is difficult for the pregnant women to accept its expensive price.Although the above methods can detect chromosome aneuploidy,but it can not determine the source of additional chromosome,and it can not detect the Down syndrome which are caused by the duplication of tiny fragment from chromosome 21. Along with the development of molecular genetics,diverse methods have been developed to detect Down syndrome.Fuentes find the Down syndrome critical region located in 21q22.1-q22.2 in 1995.STR-PCR is a popular application.Eight polymorphic short tandem repeats(STRs) locies in and near the Down syndrome critical region(21q22.1-21q22.2) on 21 chromosome were selected,and through polymerase chain reaction(PCR),polyacrylamide gel electrophories,and silver staining,Down syndrome may be detected.Compared with the method of karyotype analysis,the method of STR-PCR is fast,simple and low cost,and it can also detect the Down syndrome wich are caused by the duplication of tiny fragment from chromosome 21.It is a good help to karyotype analysis,and it is able to improve the detection rate of Down syndrome.ObjectiveTo investigate the value of STR-PCR technique in the diagnosis of Down syndrome.And then establish fast,efficient molecular methods to diagnosis of Down syndrome to help the method of karyotype analysis.Materials and Methods1.Samples 60 blood sample of Down syndrome patients verified by karyotype analysis and the blood sample of their parents;50 samples of amniotic fluid and some peripheral blood of the parents.2.Methods Eight STR were selectded wich were located in and near the core regionon on 21 chromosome.Primer sequences were obtained from GenBank.The DNA samples were extracted with Chelex method and were amplified by polymerase chain reaction technique.The PCR products were analyzed by polyacrylamide gel electrophoresis and displayed using silver staining.We can detect the Down syndrome by seeing the strain after electrophoresis.Result1.58 children with Down syndrome were detected out of 60 children with Down syndrome,the detection rate is 96.7%.2.The parental origin of the extra chromosome 21 was determined in 54 Down syndrome out of 60,with 49 inherited from mother and 5 from father.The parental origin of the extra chromosome 21 of 4 Down syndrome can not be determined.3.10 Down syndrome were detected out of 50 amniotic fluid samples.9 of them is incoincidence with karyotyping,one showed three bands in the loci of D21S1409 and D21S1433,but the result of the karyotyping is "46,XY".8 additional chromosomes and 1 chromosome fragment are gotten from the mothers,1 additional chromosome are gotten from the father.4.General the results of blood and amniotic fluid,the heterozygosities of D21S1409,D21S1433,D21S11,D21S1444,D21S1437,D21S1414,D21S1442,D21S1809 are0.69,0.84,0.88,0.81,0.75,0.79,0.82,0.68,the detection rate of Down syndrome is 30%,61%,67%,59%,43%,45%,58%,27%.If all the 8 locies are used,the detection rate is 97%.ConclusionThe eight locies show high polymorphism,the detection rate is high when all the 8 locies are used.They are valuable in the diagnosis of fetal trisomy 21,and it is a good helper to karyotype analysis.