The Study Of Detection Of Free Fetal DNA In Maternal Plasma

Objectives To study the detection method of free fetal DNA in maternal plasma.To get preparation theorically for the application of free fetal DNA information in noninvasive prenatal diagnosis of certain hereditary diseases.Methods 5ml maternal peripheral blood was collected from medium pregnancy women(16～30weeks)into one tube containing ethylenediamine tetraacetic acid(EDTA).5～10ml amniotic fluid of all the pregnant women was also collected by amniocentesis under the guidence of type-B ultrasonic.Meanwhile,2ml peripheral blood of their husband were get as comparison.Maternal blood sample swere centrifuged at 3000g,and supernatant were obtained,Plasma total DNA was extracted from medium pregnancy women by improved DNA isolation method.while the pregnant women,the husband and the fetal amniotic fluid DNA were extracted.Plasma total DNA of 10 pregnant women were processed for STR-PCR of 6 STR(short tandem repeat)loci and then the extraction efficiency and rate of assay were analyzed using DNA-PAGE (polyacrylamide gel electrophoresis)in comparison with the maternal,the husband and the fetal genome DNA.Then the Plasma total DNA of the other 10 pregnant women were processed for multiplex fluorescent PCR at sixteen different STR loci,Then the extraction efficiency and rate of assay was analyzed using ABI310 genescan in comparison with the maternal and fetal genome DNA.Results Free fetal DNA can be detected in maternal plasma.In the STR-PCR amplification part,Of all the 60 STR loci detected in 10 medium pregnancy women plasma,free-fetal DNA in maternal plasma were detected in 18 of 30 STR loci,the rate of detection was 30%. D13S317 have the maximal detection rate.In the multiplex fluorescent PCR part,Of all the 160 loci detected in 10 medium pregnancy women plasma,cell-free fetal DNA in maternal plasma were detected in 35 loci, the rate of detection was 22%.D21Sll and D8S1179 have the maximal detection rate.Different STR loci have different detecting rate,most loci which above 300bp have not results.So the the rate of detection decrease.Conelusion Free fetal DNA can be detected in maternal plasma total DNA extracted by improved DNA isolation method both through multiloci STR-PCR and multiplex fluorescent PCR,which may have expectation for noninvasive prenatal diagnosis of certain hereditary diseases.