疾病的產(chǎn)前診斷prenataldiagnosisofdisease-資料下載頁(yè)
2025-07-20 03:34本頁(yè)面
【正文】 he aspirated polar body containing a mutant allele would indicate that the primary oocyte pronucleus is carrying the normal allele. Medical Geics In both situations, only the embryos confirmed not to possess the full diseasecausing genotype are then implanted back into the uterus. Medical Geics Medical Geics Diagnostic methods Preimplantation diagnosis may be achieved using PCR, FISH or by measurement of embryonic secretory products such as certain enzymes. Medical Geics This type of analysis has been carried out successfully for the determination of fetal sex for the avoidance of sexlinked disorders such as Duchenne muscular dystrophy and haemophilia A, and for the diagnosis of single gene disorders such as cystic fibrosis, alpha1antitrypsin deficiency, TaySach39。s disease, fragile X and sickle cell anaemia. Medical Geics Worldwide, preimplantation diagnosis of embryos has been attempted on over 1,200 in vitro fertilisation cycles in 1997, with clinical pregnancy resulted in 20%. No increase in the occurrence of abnormalities has been observed in the liveborns. Medical Geics B. Noninvasive prenatal diagnosis using fetal cells isolated from maternal blood Circumstantial evidence that fetal nucleated cells exist in maternal peripheral blood can be traced back to 1969. Medical Geics However, convincing proof of the existence of these cells have to await the development of molecular biological techniques, especially the PCR. Medical Geics Using the PCR, investigators are able to demonstrate the presence of cells possessing fetal geic markers circulating in the peripheral blood of pregnant women. The isolation of these cells offer the possibility of a noninvasive and safe method for prenatal diagnosis. Medical Geics Fetal nucleated cell types in maternal blood Three populations of fetal nucleated cells are currently known to be present in maternal peripheral blood: fetal lymphocytes, trophoblasts and fetal nucleated red cells. Medical Geics At present, the isolation of fetal nucleated red cells is receiving the most attention from investigators in the field due to the availability of relatively specific monoclonal antibodies against these cells. Medical Geics Isolation of fetal cells and geic analysis A bination of physical and immunological methods are used to isolate fetal nucleated cells from maternal blood. Physical methods include density gradient centrifugation and micromanipulation techniques while immunological methods include the use of monoclonal antibodies. Medical Geics Geic analysis of these isolated fetal cells can be performed using PCR or FISH. Fetal cells in maternal blood have been successfully used on a research level to diagnose trisomy 21, trisomy 18, betathalassaemia and sickle cell anaemia. Actual clinical use will have to await further technological development to improve its reliability and clinical trials to assess the sensitivity and specificity of this approach.
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