Deoxyribonucleic acid (DNA) is the biomolecule responsible for storing and transmitting genetic information in living organisms. DNA consists of two long polynucleotide chains. Each chain is composed of repeating nucleotide units, which include a phosphate group, a five-carbon sugar called deoxyribose, and one of four nitrogenous bases: adenine (A), thymine (T), guanine (G), or cytosine (C).
DNA consists of two antiparallel strands held together by hydrogen bonds between complementary bases: adenine pairs with thymine through two hydrogen bonds, while guanine pairs with cytosine through three. This base pairing enables the formation of the double helix structure, where the sugar-phosphate backbones form the exterior and the paired bases are located inside, stabilizing the molecule. Approximately 99.9% of the DNA sequence is identical among individuals, with only about 1.2% of the human genome comprising protein-coding genes. The remaining DNA includes regulatory elements and non-coding regions that contribute to genome function and regulation.
Overview of Genetic İnformation Flow.(NVCC)
Advancements in sequencing technologies have revolutionized genomic research and clinical diagnostics over the past two decades.The cost of whole genome sequencing has decreased by more than 99.99% between 2001 and 2023, from approximately 100 million USD to just over 500 USD in the United States. This reduction has contributed to increased availability and affordability of genetic testing in healthcare applications.
Following the global advancements in genome sequencing technologies and their increasing accessibility, Turkey has also taken steps to integrate genetic diagnostic services into its healthcare system. A national regulatory framework for genetic diagnostic services was introduced in Turkey in 1998. Since then, licensed genetic diagnosis centers have been established within university hospitals, public healthcare institutions, and private clinics. As of 2024, these centers operate in more than 50 cities and provide services related to prenatal and postnatal genetic testing. Their distribution reflects the structural development of molecular diagnostic capacity within the national healthcare system.
Storage and Expression of Genetic Information
DNA contains hereditary information necessary for regulating protein synthesis in cells. Genes, specific sequences of nucleotides, encode the instructions for protein production. During transcription, genetic information is copied from DNA into messenger RNA (mRNA) with an estimated error rate of about 0.01% (1 error per 10,000 nucleotides). DNA replication, which duplicates the genome prior to cell division, exhibits a much lower error rate of approximately 0.00000001% (1 error per 10 billion nucleotides) due to proofreading and repair mechanisms. However, a small fraction of replication errors persist and can lead to mutations that contribute to genetic variation. Gene expression governs cellular functions and organismal traits, while DNA replication maintains genetic continuity during cell division.
Transcriptomic research in Turkey has been advancing through the adoption of Next Generation Sequencing (NGS) technologies combined with bioinformatics analysis. Tan et al. (2018) proposed an ensemble learning approach that integrates drug-induced gene expression profiles from cancer cell lines to predict responses to anticancer drugs, demonstrating improved predictive performance compared to earlier methods. This study exemplifies the application of transcriptomic data for pharmacogenomics and personalized medicine. Complementing this, Sarıman et al. (2020) provided a comprehensive overview of transcriptome analysis using NGS, emphasizing the technology’s capability to detect full gene and isoform expression, single nucleotide variants, insertions, deletions, fusion genes, and expression quantification. Their work outlines the bioinformatics workflows required to analyze large-scale sequencing data effectively. Together, these studies illustrate the growing integration of NGS and computational approaches in Turkey’s transcriptomic research, facilitating a deeper understanding of gene expression patterns relevant to disease mechanisms and therapeutic development.
Historical Context and Discovery
DNA was first identified in 1869 by Friedrich Miescher, who isolated a phosphorus-containing substance from the nuclei of white blood cells, later known as deoxyribonucleic acid. Its biological significance remained uncertain until 1944, when Oswald Avery, Colin MacLeod, and Maclyn McCarty demonstrated that DNA is the carrier of genetic information. In the early 1950s, Erwin Chargaff established empirical base-pairing rules, showing that DNA contains equal ratios of adenine to thymine and guanine to cytosine, suggesting a regular structure. The elucidation of the DNA double helix in 1953 by James Watson and Francis Crick represented a critical turning point in molecular biology. Their model, which proposed two antiparallel strands held together by specific base pairing, was constructed based on key X-ray diffraction data generated by Rosalind Franklin and Maurice Wilkins. Franklin’s X-ray crystallography was instrumental in defining the helical parameters of DNA, and her data provided essential evidence for the correct helical geometry. Watson and Crick’s model not only accounted for Chargaff’s rules and structural symmetry but also explained the molecular mechanism of DNA replication with remarkable conceptual clarity. Together, these foundational contributions established the structural and functional framework for modern genetics.
Genetics research in Turkey began predominantly after the 1950s, initially concentrating on cytogenetics, biometrics, population genetics, and mutation genetics. Attempts to organize geneticists occurred in the late 1970s, but these efforts were short-lived. Following support from TÜBİTAK, advancements in cytogenetics and molecular genetics were observed after the mid-1980s, coinciding with the return of personnel trained abroad who introduced new methodologies. Universities established central laboratories, including BİYOGEM at Istanbul University and the Biotechnology Center at Atatürk University. Techniques such as RFLP, RAPD, PCR, in situ hybridization, isozyme analysis, and PAGE have since been employed in DNA and protein research. Emphasis has shifted from developing novel methods to the practical application of existing techniques. Research activities across various fields have been cataloged based on date, researcher, and topic according to current records.
Advances and Applications
Advancements in genome sequencing technologies, such as next-generation sequencing, have greatly enhanced the ability to analyze DNA sequences rapidly and cost-effectively. This progress has accelerated genomic research, enabling projects like the Human Genome Project, which mapped approximately 99% of the euchromatic portion of the human genome with high accuracy. Applications of DNA knowledge are broad and transformative. In medicine, DNA analysis allows for genetic diagnosis, which is most commonly applied in cancer treatment, as well as personalized medicine tailored to individual genetic profiles, and gene therapy aimed at correcting defective genes. In biotechnology, genetic engineering enables the development of genetically modified organisms (GMOs) for agriculture and industrial use. DNA fingerprinting is widely used in forensic science for identification purposes. Additionally, advances in synthetic biology involve designing and constructing new genetic sequences for various scientific and therapeutic purposes. These ongoing developments continue to expand the understanding of DNA’s role in biology and open new avenues for innovation in health, agriculture, and environmental sciences.
DNA Technologies and Their Applications (Image generated by AI)
Genetic and cellular therapies in Turkey have seen development within regulated and research-focused institutions. A study conducted by the Department of Forensic Medicine at Fırat University investigated DNA fingerprinting techniques using various biological samples, including blood, hair follicles, saliva, nails, and semen, highlighting their application potential in forensic identification. The results demonstrated variable DNA yields across sample types, confirming the feasibility of incorporating such analyses into routine forensic practice. Concurrently, Ankara University’s Stem Cell Institute, established under the 2009 Council of Ministers Decree, operates as the country’s first and sole institution equipped with Good Manufacturing Practices (GMP)-certified advanced laboratories for cellular therapy research. The Institute conducts experimental and clinical studies in areas such as immunodeficiency, resistant gastrointestinal disorders, cancer, and tissue repair. It emphasizes compliance with regulatory standards to ensure safety and efficacy before clinical application. Current research includes the production and clinical testing of stem cell-based therapies, tissue engineering, cancer vaccines, and recombinant drug development. These institutional efforts exemplify Turkey’s growing infrastructure and commitment to advancing molecular and cellular medical applications within both forensic and therapeutic contexts.
