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Single Gene Diseases and PGD
A great number of single gene diseases can be defined in the embryos with PGD today. Detailed preliminary preparation is needed in order to make definition in the embryos. Mutation (disorder) that causes the genetic disease is detected by taking blood from mother, father and, if available,sick child. If the mutation is already detected, then it is confirmed.
Biological agents (short DNA fragments) called as primers are designed in order to increase the genetic part for genetic diagnosis in embryos. Primers are tried in single cell (lymphocyte, in-cheek cells) and working conditions are optimized and embryos are prepared for the PGD process.
It is necessary to comply with the instructions in the international standards and take safety measures (to work with double blastomers, study the polar body with blastomer, confirm the results obtained from the genetic part with the indicators called as marker) in order to overcome the global problems caused by the technique (ADO-Alel Drop Out, contamination, amplification failure, recombination) and be sure about the safety of the results.
The blastomers (embryo cells) taken with the biopsy are analysed with a method called as PCR. This method is based on the principle of reproducing the genetic part in millions of copies in order to detect the mutation, or disorder, that causes the single gene disease in the family also in the embryos. It is important to prefer a method that can give quick, easy and safe results for the detection of mutations after the PCR. The most appropriate method for this aim is the Minisequencing method that is preferred by many PGD centers around the world. Because this method provides the detection of mutations more than one together and at the same time, it is also preferred by our center.
It is important to diagnose as soon as possible by considering the fact that embryos can survive outside for a limited time. Diagnosis can be generally made within 1-1,5 days. For this, it is necessary to use the latest technology Genetic Analysors and analysis methods which can be applied quickly and easily. Right diagnosis is very significant in PGD process. It is necessary to take compulsory measures to remove the risk of misdiagnosis. Two negative control and a positive control at least should be included in the study. The results obtained with mutation analysis should be confirmed with a second method that can work at the same time. The method called as connection analysis is used for this. An embryo that has a diagnosis doubt should not be transferred. Embryos chosen for transfer should be the embryos which are confirmed with both mehtod in terms of their health and do not have any contamination suspection.