Genetic Polymorphisms Of 5 Short Tandem Repeats (STR) Loci On Chromosome 21 And Chromosome 18 In Han Population Of Kunming Regain And The Application Of STR In Prenatal Diagnosis

Objective: (1) To elucidate the genetic polymorphisms of 5 STR loci onchromosome 21 :D21S11,D21S1435,D21S1437 and chromosome 18 :D18S1002,D18S499 in Han population of Kunming regain and construct a preliminarydatabase for genetic analyse.(2) To discuss the feasibility of prenataldiagnosis by using STR, and establish the rapid prenatal diagnosissystem. Method: (1) 160 EDTA blood specimens and 40 amniotic fluid andmaternal blood specimens were collected from unrelated individuals inKunming regain .The DNA were amplified by PCR. The PCR products wereanalyzed by polyacrylamide gel electrophoresis(PAGE), followed by silverstaining, and the allele size was detected by Image Analysis System. Forthe five STRs, the distributions of genotypes were determined byHardy-Weinberg equation. (2) 11 Down' s syndrome(DS) samples,2 DSfamilies,1 Edward syndrome(ES) samples and 50 familise undergoingprenatal diagnosis were collected for STR analyse using the same methodmentioned before. About 2 DS families, diagnosis were made for the parental origins of extra chromosomes and the stages of nondisjunction,and the result of STR analyse were contrast with the amniocentesis.Result: The polymorphism information content of the 5 STRs was all over0．50, and was accorded with Hardy-Weinberg equation. The analyse of 40amniotic fluid and maternal blood showed that the fetal DNA were not mixedwith maternal DNA using chelex method, and accorded with Mendel' s law.1 sample showed mutation in D21S11．(2) D21S11,D21S1435,D21S1437,D21S2039,D21S1411,D18S1002,D18S499,D18S386,and D18S535 were used forprenatal diagnosis , and the results were consistent with amniocentesis. 2DS families revealed that the parental origins of extra chromosomes wereboth come received from mater, and the stages of nondisjunction were MI.50 prenatal diagnosis families revealed that 48 cases were normal, and1 case was diagnosed ES, and lease was lost because the maternal DNA wasmixed with the fetal DNA. Conclusion: (1) The obtained data can not onlybe used a s evidences for genetic diagnosis of DS, but also for calculatingthe probabilities in the paternity test and individual identification.(2) Using STR could not only diagnose DS,ES quickly and exactly, but alsocould determine the parental origins of extra chromosomes and the stagesof nondisjunction. Multi-STR was more efficiency compared with only oneSTR. When amniotic fluid was mixed with maternal blood, it would likelyto make a wrong conclusion.