July 6, 2022
Shahid Sadoughi University of Medical Siences
Pre-culturing Genetic Tests

Pre-culturing Genetic Tests (PGT)

PGT (pre-culturing genetic testing):

1. Diagnosis of sex therapy in fetuses before implantation using FISH technique.

2. Evaluation of disorders of a number of chromosomes before implantation.

3. Investigation of chromosomal aneuploidy using 24Sure CGH array technique, (sample sending).

4. Investigation of monogenetic mutations using NGS technique (sending sample).

Pre-implantation Genetic Diagnosis (PGD)

Pre-implantation genetic diagnosis (PGD) is a technology in the science of reproduction that has been considered to increase the likelihood of pregnancy and reduce fetal genetic disorders. This technique is used to identify genetic defects and prevent the transmission of certain diseases or genetic disorders to the fetus. It is carried out by preventing the transmission of embryos with genetic diseases to which couples are exposed, as well as for the selection of a particular sex in certain diseases. Embryos examined for PGD are usually present during the IVF process. In fact, using this technique, all genes present on 23 pairs of fetal chromosomes are examined and defective genes that carry inherited diseases are identified, thereby transmission and formation of infected fetuses, as well as the birth of children with genetic disorders is prevented.  PGT includes two techniques: PGD and PGS. Genetic screening in these two methods is to examine the chromosomal abnormalities of the fetus.

Pre-implantation Genetic Screening (PGS): A screening process that ensures that a number of normal chromosomes are present and detects potential genetic abnormalities.

Pre-implantation Genetic Diagnosis (PGD): Cells from the embryo to test for specific genetic conditions before the embryo is transferred to the uterus.

CGH Array

This test is called a molecular karyotype and is especially used to identify the cause of mental retardation or congenital anomalies, and is a high-resolution technique for examining deletions or additions throughout the genome and identifying chromosomal imbalances. Because this technique is able to detect deletions and additions in the range of 5 to 10 kHz, it is called the Microarray Comparative Genomic Hybridization (CGH array).

The advantage of this method over the previous methods is that in the traditional methods, many chromosomal deletions that are about 3 to 5 megabases in size are not detected because these methods use a microscope and the ability to distinguish deletions and add power. Microscope resolution is limited. As a result, the changes are much smaller than the microscopic detection power, which is not detected by invisible changes. In addition to high resolution, the lack of time-consuming cell culture techniques speeds up the process.

Another advantage of this test over techniques such as FISH and QF-PCR is the comprehensiveness of the CGH Array test. Chromosomal deletions are also detected in the FISH technique. However, this technique is used when clinical signs suggest the possibility of a chromosomal disorder, and only one gene or a known part of the genome is examined. Nonetheless, the CGH Array test, regardless of the clinical signs, makes it possible to examine a large number of deletions and additions with just one test. The disadvantage of the Array CGH method is that it does not detect balanced chromosomal displacements. In this case, no part of the chromosome is removed or added. Rather, only the displacement of parts of the chromosome is the cause of the disease, so the CGH Array is not able to detect it.
تاریخ بروزرسانی: 1401/04/13

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