文献_Preimplantation Genetic Diagnostics A Review.pdfVIP

Preimplantation Genetic Diagnostics: A Review R. Jordan Williams Introduction: Preimplantation genetic diagnostics (PGS/PGD) refers to the “determination of the nature of a pathological condition or disease in the ovum; zygote; or blastocyst prior to implantation. Cytogenetic analysis is performed to determine the presence or absence of genetic disease”(MeSH). PGD evolved as an “alternative to prenatal diagnosis to reduce the transmission of severe genetic disease for fertile couples with a reproductive risk”(Braude). In comparison with prenatal testing—which includes such procedures as amniocentesis, chorionic villus sampling, and cordocentesis; all of which are various procedures that sample fetal tissue or blood from either the amniotic sac, placenta, or umbilical cord—clients can avoid issues regarding pregnancy termination since the embryo is screened prior to implantation in the uterus. Overall, the set of methods available for PGD involve techniques used for assisted reproductive technologies as well as general genetic testing; including PCR, FISH, karyotyping, and even genetic sequencing. This paper reviews selected methods involved in the process of PGD, current applications with regard to specific diseases, and ethical considerations. Methods: Preimplantation genetic diagnostics involves three primary stages. First, embryos or gametes must be collected. In this way PIGD is inherently tied to the use of assisted reproductive technologies (ARTs) such as ovarian stimulation, in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Second, the collected cell or cells must be biopsied in order to extract their genetic material; which can subsequently undergo various genetic tests. Generally fertilized embryos are biopsied for analysis, and a few different biopsy options will be described here. Lastly, the genetic material is a