Whole Exome Sequencing

Our entire DNA consists of approximately 20,000 genes. Genes are packed on chromosomes. A person usually has 23 double chromosomes or 46 chromosomes in total. This entire DNA collection is called a genome. The examination of the packed state, namely the chromosomes, is done by Cytogenetic methods by Medical Genetics.

Non-functioning genes can cause disease. There are different ways to study DNA. Usually a technology called sequencing is used. Sequencing reads “reads“ each letter of DNA and finds changes (variations or mutations) in our genes that may cause disease or affect a disease risk. The so-called DNA sequencing method is an advanced technique used to test for genetic disorders in the sequence of DNA building blocks (nucleotides / bases) in the individual's genetic code. There are two methods for identifying genetic variations in the individual or patient's DNA sequence. These include:Whole Exome Sequencing (WES) and Whole Genome Sequencing (WGS). It is increasingly used in health services and research; Both methods are based on new technologies that allow rapid sequencing of large amounts of DNA. These approaches are known as Next Generation Sequencing (NGS).

The original sequencing technology (the name of the scientist who developed it, Frederick Sanger), called the Sanger sequence, was a discovery that helped scientists identify the human genetic code, but it was time-consuming and expensive. The Sanger method has been automated to make it faster and is now used to sort short DNA fragments in laboratories, but sequencing can take years to process a person's DNA (known as the person's genome). NGS has sped up the process while reducing the cost of a human WGS.

With next-generation sequencing, it is now possible to sequence large amounts of DNA (for example, the Whole Genome of an individual or all parts of his DNA that instructs to produce proteins), namely the Whole Exome, in a short time and at an affordable price.

Whole Exome Sequencing sequences the entire exome, that is, all protein-coding parts (exons) that are thought to make up 1% of the genome. This method allows to study genetic variations (mutations) in the protein coding region of all genes rather than just a few selected genes. Since most of the known disease-causing mutations occur in exons, whole-exome sequencing is considered an effective method for identifying possible disease-causing mutations.

With Whole Genome Sequencing, a large deal of genetic information can be closely looked at by sequencing or "reading" all bases in DNA (genome). The sequence of the whole genetic code of a person is called whole genome sequencing. Researchers have found that DNA variations in intron regions between the exons outside the exon can affect gene activity and protein production, and may lead to genetic defects. This method is recommended in cases where all exsomposition is performed and the results are normal.

Sequencing of Gene or Target Regions. Since the genome is much larger, exome can be sequenced at a lower cost and at a greater depth (number of readings of a particular nucleotide). Larger depth provides more confidence in rarely detected low frequency or first-time changes. In some cases, special panels can be used, which gene panels contain a number of selected genes associated with diseases previously suspected by your doctor, or mutations that contribute to the formation of diseases. The sequencing of the selected genes and target regions can be sequenced with lower costs and even more depth due to the shorter readings.

While more genetic alterations than the sequencing of the gene or target regions can be detected by whole exome and whole genome sequencing, the importance of most of these changes is unknown. Since all genetic changes do not affect health, it is difficult to predict whether defined variants are disease-related.

All the exome and all genome sequencing that lead the clinicians to the diagnosis are also valuable tools for researchers.