Rapid Prenatal Detection Of Down Syndrome By Homologous Gene Quantitative PCR

IntroductionDown syndrome is the main reason that cause congenital human intelligence defect, about 95% caused by the fact that the chromosome 21 is not separated at the time of the meiosis , transposition type account for 3 - 4% , chimera account for 1 ~2% , the others is it amalgamate person who store to inlay for transposition. But in recent years with deeply learning of the etiology to Down syndrome, 2% -3% Down syndrome their chromosome 21 is not triploid, but the key area of pathogenic gene of Down syndrome (Down's syndrome critical region) , take place chromosome " the disguise repeat " ( cryptic duplication ) . In this case, patient's with symptom of Down syndrome and physical sign, but the caryotypeis analysis often very difficult to find abnormily. therefore, it is not enough to diagnose accurately all Down syndrome patients with the caryotypeis analysis of chromosome. There are also some method to determine mother blood a -fetal protein , chorionic - gonadotropin hormone or estriol , etc. Screening Down syndrome, but these methods are not to diagnose Down syndrome directly, it is relatively low to detect Down syndrome. We utilize D21S1409 and D21S11 STR polymorphism examine the gene through quantitative PCR technology to detect Down syndrome, but this method cant detect homozygote as above STR site, it is at the same time difficult to diagnose the chimera.Homology gene quantitative PCR ( HGQ - PCR) utilize one pair of primer proceed PCR amplification to measure human cell if some chromosome have triploid, or the situation that the gene ( segment) deletion. This technology is to set up one to contrast inwards in the same test tube, the positive contrast which it can already increase as PCR, can measure target array quantity consult inside.Materials and MethodsThe periphery blood of 178 normal person; 38 cases of Down syndrome ( 14/21 transposition and 21/21 transposition respectively two, other 34 are trip-loid ) ; 22 cases of amniotic fluid ( pregnant 16-20 weeks ) and 20 pregnant women periphery blood (pregnant 9-21 weeks ) ; It has amniotic fluid and periphery blood of 2 pregnant woman which suspected conceive Down syndrome foetus .This experiment uses the saturated sodium chloride to draw blood leucocyte DNA, boil to draw amniotic fluid DNA come off cell, micromanipulation to obtain individual nucleated red blood cell(NRBC). HGQ -PCR, which can directly detect the additional copy of chromosome 21 by comparing simultaneously amplified two highly homologous genes, e g; the human liver - type phospho-fructokinase located on chromosome 21 critical region of Down syndrome (PFKL - CH21) and the human muscle - type phosphofructokinase located on chromosome 1 ( PFKM - CH1) , Fluor Chem V2. 0 Stand - Alone software analysis PCR result ratio. Use the quantitative analysis of PCR - STR to improve the diagnosing rate of Down syndrome and accuracy futher.Results:178 normal controls and 38 clinically diagnosed Down syndrome patients The ratios of PFKM - CHl/PFKL - CH21 products were 1.40 ±0.367 ( mean ± SD ) and 0.46 ±0.21 ( mean ± SD) for disomy 21 and trisomy 21, respectively. 22 cases of normal amniotic fluid cell DNA proceed PCR amplification the ratio of products range from 1.23 to1.45. The normal foetus nucleated red blood cell DNA separate from 20 persons of gravida periphery blood that are used in the homology gene quantitative PCR to measure after the whole genome amplification (WGA) , the ratio range is 1.12 -1.68. We found that the PCR results of am-nictic fluid and foetus nucleated red blood cell DNA from 2 pregnants suspected carry on Down syndrome foetus are close close each other. The first one is 0.56...