DNA is made up of molecules that we call nucleotides. Each nucleotide; It consists of a Phosphate group, a Sugar group and a Base group. These 4 Base groups, which are the basic building blocks of DNA; It is named Adenine (A), Guanine (G), Thymine (T), and Cytosin (C). The sequence and sequence of these 4 base letters constitute the information in DNA, that is, our genetic code. Each person has a unique genetic code, GENOM. We can call this GENOM one’s own book. The entire human GENOM consists of 3 billion 200 million letters A, G, T, C unique to each person, and these letters make up about 30,000 GENs.
FUNCTION OF GEN
Each gene is a unique piece of DNA responsible for protein synthesis. Since enzymes are made of proteins, each gene synthesizes one enzyme. This situation is called the One Gene, One Enzyme Hypothesis. Because enzymes catalyze chemical reactions unique to each other, genes determine and direct enzyme activities. If a gene changes due to a mutation, this can cause problems in enzyme synthesis. If an enzyme is not synthesized properly, the organism will either get sick or die.
DNA SEQUENCE ANALYSIS
DNA sequencing is one of the most important technologies developed for genetic research. This technology allows researchers to identify the sequence of letters in DNA fragments.
The first DNA sequencing method in history was developed by Frederick Sanger and his friends. This method has opened the “Human Genome Project” field between 1990 and 2003. With this project, the entire human genome has been obtained by sequencing. Thanks to this technology, researchers have had the opportunity to examine molecular sequences for many diseases.
Although the Sanger method is a breakthrough technology in the history of genetics, it is costly and time consuming. The disadvantages of this method have encouraged researchers to develop cheaper and faster methods. With these efforts, gene sequencing efficiency was increased and “Genome-Wide Partnership Studies” started in the early 2000s. Thanks to these studies, more than 25 thousand genes related to diseases have been discovered.
In the mid-2000s, the first series of Next Generation Sequencing (NGS) devices entered the market. Further development of these devices has enabled researchers to examine only the gene region of interest.
In sequence analysis; The more exons the gene has, the longer it takes to sequence that gene. This method is similar to searching for a home address on a street, if we consider the streets to be genes, the streets to be exon, and the houses to point mutations, the longer and more streets the street consists of, the more time and cost-effective it is to find the address. Therefore, sequence analysis for each gene costs different time and cost.
Deletıon And Duplıcatıon Analysıs
If the diagnosis cannot be made by sequence analysis, gene losses (Deletions) or gains (duplication) in the gene should also be looked at. For this purpose, different methods such as MLPA and Gap PCR are used. In the example of home address, deletions define dilapidated or destroyed houses, and duplications describe houses with illegal floors.
Both Sequence Analysis and MLPA deletions and duplications need to be checked for the exact identification of a gene.
The patients who applied to our center; A detailed report containing detailed clinical information, all previous tests and family tree is prepared, after giving detailed information about the tests, the consent documents are signed, and then analyzes are made on the blood samples taken from the person.
After getting the results, a detailed interpretation of the results is made and genetic counseling is given. In addition, the physician of the follow-up patient is discussed, after mutually discussing the clinical and molecular aspects of the patient, the diagnosis of the person becomes clear and the treatment method is determined more clearly by the physician.