Preimplantation genetic diagnosis (PGD) is a procedure used in embryos obtained through in vitro fertilization. There are three main techniques of PGD: FISH (fluorescence in situ hybridization), PCR (polymerase chain reaction) and haplotyping. Haplotyping is the latest developed technique and involves the use of DNA fingerprinting, which can detect the possible chromosomes with defective genes.
The first records of the used of haplotyping in preimplantation genetic diagnosis were in 2006, in London. Improvements have been brought to the technique and today it is commonly used in embryos obtained in the process of in vitro fertilization. The procedure is considered superior to the other types of PGD.
What Is Haplotyping
Haplotyping, also known as preimplantation genetic haplotyoping, is a method to detect whether there are any genetic abnormalities in an embryo obtained through an IVF method. The procedure employs DNA profiling or fingerprinting, which will give the genetic profile of the embryo. The genetic profile is a set of numbers, and genetic abnormalities can be identified through this procedure. If there are genetic abnormalities, the embryo may not be implanted, and the IVF cycle can be repeated until a healthy embryo is obtained.
The test is recommended for couples that may have genetic predisposition to certain diseases or have certain diseases in the family. The PGD can also be used in couples that are not likely to have genetic defects in their DNA, but would like to be sure the embryo that is implanted is healthy.
Haplotyping Compared to Other PGD Techniques
Haplotyping has been found more efficient and give more accurate results than the other types of preimplantation genetic diagnosis. Haplotyping can be used on male embryos, while the other two PGD techniques cannot do this. When both the male and the female embryos are tested, this can make sure that the embryos are healthy; when there are several healthy embryos, these can all be inserted, which will increase the chances of successful implantation and pregnancy.
Male embryos can be tested for X-linked disorders (i.e., Becker's muscular dystrophy and Duchenne muscular dystrophy). The haplotyping can give a higher accuracy rate when establishing the health of the embryos, which will result in reduced chances of genetic defects in the babies resulting from IVF.
Haplotyping and Diseases It Detects
Haplotyping is a preimplantation genetic diagnosis which can identify the following genetic diseases in the IVF embryos:
- Huntington's disease, an incurable disease that leads to premature death
- Cystic fibrosis, also incurable and will result in premature death
- Becker's muscular dystrophy
- Duchenne muscular dystrophy, which will develop into muscle degeneration, rendering the patient unable to move and will lead to death
- X-linked disorders
- Alport's syndrome, which causes advanced kidney disease and hearing loss
- Sickle cell disease, resulting in reduced life expectancy
- Von Hippel Lindau disease, an untreatable disease that manifests through the presence of small tumors or hemangioblastomas in various areas of the body