What is whole exome sequencing and whole genome sequencing?
Determining all of the genetic mutations that cause genetic diseases is a significant challenge for both physicians and patients, particularly for rare or difficult-to-diagnose genetic diseases that can take years to diagnose using traditional screening techniques, leading to postponements in the patient's condition as well as high costs. However, as the field of genetics medicine continues to advance, what is known as next generation sequencing techniques have emerged to speed up the process of identifying all genetic mutations or changes in just a few days and at the lowest possible cost, to be the most powerful tool in the era of precision medicine.
In this article, we will discover the two most important and widely used tools in next-generation sequencing technologies, whole exome sequencing and whole genome sequencing, as well as the differences between them.
What exactly is whole exome sequencing?
The human genome, or DNA, is made up of 180,000 small pieces called exons that direct the body to produce proteins necessary for its health, such as hemoglobin. Exons cluster together to form exomes, which account for only 1% of the total human genome (approximately 20,000 genes).
Whole exome sequencing detects potential changes in exome sequences that could lead to more than 7,000 genetic diseases, such as:
1. Congenital anomalies.
2. Growth problems and learning difficulties.
3. Autism.
4. Mendelian disorders (caused by a mutation in a specific gene), such as sickle cell anemia, hemophilia, deafness, blindness, and others,
5. Hereditary obesity.
6. Muscular dystrophy, such as Duchenne disease.
7. Hereditary metabolic diseases, such as hypercholesterolemia and Niemann-Pick disease.
8. Cancer, including breast cancer, ovarian cancer, and more.
What are the benefits of whole exome sequencing?
1. Whole-exome sequencing informs couples or prospective couples if they are carriers of genetic mutations that could lead to the emergence of genetic diseases in their children in the future (carrier status).
2. Faster and less expensive detection of genetic mutations.
What are the drawbacks of whole exome sequencing?
Despite the whole-exome sequencing's effectiveness in diagnosing diseases faster and at a lower cost, one of its main drawbacks is that it does not include examining the entire human genome, thus does not cover all changes in genes that may lead to other genetic diseases.
What exactly is whole genome sequencing?
Whole-exome sequencing, as previously stated, covers changes that occur in only 1% of the human genome or DNA, implying that it does not cover all possible changes in the human genome. As a result, there was a need for a new genetic test that covered all possible changes in the entire DNA.
Whole genome sequencing is the most comprehensive next-generation sequencing (NGS) technology, examining all 3 billion genetic letters of DNA to create a massive database that allows us to identify 7,500 genetic diseases and help diagnose diseases that are unknown or difficult to diagnose. However, it is more expensive than whole exome sequencing.
Among the genetic diseases discovered by whole genome sequencing are, but are not limited to:
1. Leukemia, pancreatic cancer, bone cancer (sarcoma), breast cancer, and other cancers.
2. Heart disease that runs in families.
3. Autoimmune diseases, such as diabetes, multiple sclerosis, and rheumatoid arthritis.
4. Kidney disease, which can lead to kidney failure.
5. Neurological diseases such as epilepsy, Parkinson's disease, Huntington's disease, dementia, and other conditions.
6. Diseases that are uncommon or unknown.
Along with the genetic diseases addressed by whole exome sequencing.
What are the benefits of whole genome sequencing?
In addition to diagnosing all possible genetic diseases, including those with unknown causes, by examining the entire DNA, whole genome sequencing aids in:
1. Determine if you have a food allergy
Knowing which foods are suitable for you and which are not suitable for you and may cause allergies and other diseases such as obesity, type 2 diabetes, heart disease, and cancer in the future, based on your genetic makeup.
2. Pharmacogenomics
You may take a flu medicine and not feel better, whereas your friend may take the same medicine and feel much better. The reason for this is that we all have different genetic makeups; you may get a drug to treat a disease but you didn't get better, and it may cause side effects as well as other complications, whereas it works for someone else.
As previously stated, whole genome sequencing provides a comprehensive database of your DNA that assists physician in determining appropriate and inappropriate treatment based on a person's genetic make-up, particularly for cancer patients. Genome sequencing could completely alter their treatment plan.
For example, radiotherapy should be avoided in patients who have a mutation in the TP53 gene, which can lead to leukemia, breast cancer, and other cancers. Because it increases the risk of developing another type of cancer.
He may also persuade the doctor to discuss targeted cancer therapy with the patient, which involves drugs that target the genes responsible for cancer cell development and spread.
3. Prevention of infectious disease transmission
Whole genome sequencing also aids in the control of infectious diseases by providing insight into the genetic makeup of pathogenic fungi and microbes, as well as how they are resistant to antibiotics, allowing for the development of more effective treatments.
What are the drawbacks of whole genome sequencing?
1. One of the most noticeable disadvantages of the whole genome sequencing is its high cost, which increases by 2-3 times when compared to the whole exome sequencing.
2. It takes longer to analyze than the whole exome sequencing because it covers all of the DNA.
Finally, the best genetic test for you is determined by your medical history and the recommendations of your physician and geneticist. Each test has advantages and disadvantages in diagnosing genetic diseases to ensure better health for you and your family.