The embryos are obtained through ivf
with micromanipulation. Once the developing embryo reaches a developmental stage of about 8 cells (on the third day after fertilization), a single cell is removed from each embryo after a minimal incision is made in the envelope under the microscope, and a genetic diagnosis is made to reveal the presence of abnormalities in the number or chromosomes or genes. The diagnosis is usually received on the day of the test and afterwards the embryos that were tested and found healthy are returned to the uterus.
The pre-implantation diagnosis is assisted by two basic methods of diagnosis. One is called FISH, through which the pattern and number of chromosomes (genetic cargos) in the cells of the embryo are identified. This method can determine the sex of the fetus (the presence of chromosome X or Y), Down syndrome (three chromosomes 21 per embryo instead of just two), and problems with re-combination of the genetic information between the chromosomes (translocation).
The second diagnostic method is PCR, which can identify embryos with a genetic disorder due to a specific deficiency of a in a sequence on genetic information in the chromosomes. This category can include diseases such as cystic fibrosis (CF), Tay-Sachs, Familial Dysautonomia and various muscular diseases