Next Generation Sequencing (NGS)
NGS is the special technique in detecting abnormalities of a gene deep to its base sequences, the smallest component of one chromosome, by comparing these sequences of abnormal gene to the normal one. Normally, a human body consists of 23 pairs of chromosomes and, as aforementioned, each of the chromosomes contain genetic materials essential for the organism to develop and grow and to function properly. One chromosome consists of genes, and each of these genes consist of amino acids containing a great amount of base sequences. This means that one abnormal or mutated gene can inevitably pass body disorders and malfunctions from its inheritor to its offspring.
Therefore, this technique can be highly accurate in detecting the abnormalities occurring in any genes, and is now applied to pre-implantation genetic screening (PGS), one of the best means for diagnosis in the present.
The advantage of performing PGD with NGS is that the result of diagnosing abnormalities in all 23 pairs of chromosomes can be 99.9% accurate.
Pre-Implantation Diagnosis (PGD)
PGD (Pre-Implantation Diagnosis) refers to the diagnosis of a specific genetic defect (AKA mutation) which can cause significant health risk to the offspring, like Major Thalassemia, Sickle cell disease, Cystic fibrosis and many other diseases. It is usually offered to couples who were diagnosed by genetic studies to carry the “mutation” or already have affected children with the disease. This means that we transfer into the uterus only healthy embryo(s), which do not carry the mutation.
This procedure involves removing a small number of cells from embryos to identify genetic defects. Generally, we will remove embryo cells during cleavage (3 days’ growth) or blastocyst (5 days’ growth) to identify genetic defects.
Who might benefit from PGD?
In general, there are 5 groups of patients undergoing fertility treatment
That are recommended to do PGD:
1. Patients having treatment when the female age is over 35 (Advanced Maternal Age: AMA).
2. Patients that have had IVF failure.
3. Patients knowing that themselves or any of their family members has any genetic disease.
4. Patients that have chromosomal translocations.
5. Patients that have had recurrent miscarriages.