Preimplantation Genetic Testing
for Structural Rearrangements (PGT-SR) for Translocation and Chromosomal Rearrangements
PGT-SR identifies structural chromosomal abnormalities caused by rearrangements, including translocations, inversions, deletions and duplications, prior to achievement of a pregnancy.
Understanding Translocations Chromosome Rearrangements
Chromosomes are the blueprints of our body and are important for healthy development. They are the structures in our cells that carry our genetic information (genes).
Most individuals have 46 separate chromosomes in each of our cells, which come in 23 pairs (including pairs 1 through 22 and then XX for female or XY for Male; One copy of each chromosome is inherited from the egg, and the other from the sperm.
Different types of Chromosomal Rearrangements include:
Translocation: segments of two chromosomes break off and exchange places
Inversion: a segment of a chromosome breaks and reverses orientation
Deletion: a segment of a chromosome is missing
Duplication: an extra segment of a chromosome exists Insertion: a segment of a chromosome is inserted but into the incorrect location
Benefits of PGT-SR
PGT-SR refers to genetic tests conducted on embryos. Typically the couple has a previously identified translocation, inversion, or other chromosomal rearrangement. In conjunction with an In Vitro Fertilization (IVF) cycle, these tests identify chromosomal abnormalities in an embryo, prior to achievement of a pregnancy.
PGT-SR enables embryo(s) not having the arrangement to be identified and selected for transfer. This avoids a failed implantation, miscarriage and/or the birth of a child with multiple congenital anomalies, resulting from an unbalanced chromosome translocation.
Individuals who carry a balanced translocation or inversion may have all the correct genetic information, but found in a different position than expected. These individuals are typically healthy, but are at increased risk for infertility, miscarriage, stillbirth, or having a child with a chromosome abnormality.
PGT-SR allows selection of embryo(s) that has the correct amount of genetic material and embryos that have extra or missing genetic material as a result of the translocation or rearrangement.
Reproductive Genetic Innovations offers PGT-SR for chromosomal rearrangements, which includes 24-chromosome PGT-A, using Next-Generation Sequencing and state-of-the-art technologies if needed.
PGT-SR is performed on embryo biopsy samples. Following an egg (oocyte) retrieval and fertilization, one or more cells are removed from a blastocyst (day 5/6 embryo), then transported to RGI’s lab for PGT-SR analysis. PGT-SR for translocations typically does not require the submission of any parental blood samples or work-up prior to testing. This is determined on a case-by-case basis, upon review of the translocation report.
Developments in Next-Generation Sequencing for chromosomal rearrangements (PGT-SR) is used for detection of rearranged translocated fragments no smaller than 4-5 Mb. The method detects not only unbalanced embryos, but also identifies aneuploid embryos. For smaller fragments, the development of a special design will be required, which should be discussed in advance.
Reproductive Genetic Innovations offers testing for all 24 chromosomes, using Next-Generation Sequencing and state-of-the-art technologies with the capacity to test all the chromosomes.
PGT-A is performed on embryo biopsy samples. Following oocyte (egg) retrieval and fertilization, one or more cells are removed from a blastocyst (day 5 to 6 embryo), transported to RGI for PGT-A analysis. PGT-A does not require the submission of any parental blood samples or work-up prior to testing.
In Next-Generation Sequencing the DNA sequence of the embryo biopsies is directly analyzed. This determines whether there are extra or missing copies of the whole or part of chromosomes. The optimal accuracy is 98%, when performed on a blastocyst (day 5/6) embryo biopsy.