Genetic engineering has contributed to a fundamental transformation in modern medicine by shifting medical practice from traditional symptom-based treatment to a precise scientific approach that targets the molecular causes of disease. Advances in genetic analysis and gene-editing technologies have enabled the development of highly accurate early diagnostic tools, as well as innovative gene-based and targeted therapies that have revolutionized the management of many genetic, chronic, and oncological diseases. This article aims to highlight the pivotal role of genetic engineering in modern medicine, focusing on its major diagnostic and therapeutic applications, while also discussing the ethical and scientific challenges associated with its use. Keywords: Genetic engineering, modern medicine, molecular diagnosis, gene therapy, personalized medicine. ________________________________________ Article Medical sciences have witnessed rapid advancement over recent decades due to significant progress in genetics, particularly genetic engineering, which has provided a deeper understanding of the human genetic structure and its relationship to health and disease. This progress has reshaped traditional medical concepts, as disease is no longer viewed merely as a general functional disorder, but rather as the result of precise disturbances at the genetic and molecular levels within cells. Genetic engineering relies on advanced technologies that allow for the study, analysis, and manipulation of DNA, whether through correcting defective genes, introducing functional genes, or silencing genes responsible for disease development. This approach has significantly advanced molecular diagnosis, which is now considered one of the most accurate methods for disease detection. For example, genetic testing has made it possible to diagnose hereditary disorders such as thalassemia and sickle cell anemia at very early stages, including prenatal diagnosis, thereby enabling preventive intervention and reducing future healthcare burdens. In the field of oncology, genetic analysis of tumors has enabled the identification of mutations responsible for uncontrolled cancer cell growth, facilitating more precise cancer classification and the selection of the most appropriate treatment for each case. Cancer diagnosis today is no longer based solely on histological location, but also on the genetic profile of the tumor, representing a fundamental shift in modern medical practice. On the therapeutic level, genetic engineering has led to the emergence of gene therapy, which is considered one of the most advanced medical achievements of the modern era. This therapeutic approach is based on correcting the genetic defect responsible for disease by introducing a functional copy of the gene into the patient’s cells or modifying the defective gene itself. Gene therapy has demonstrated notable success in treating certain inherited immunodeficiency disorders and blood diseases, in addition to promising clinical trials targeting complex neurological and muscular disorders. Genetic engineering has also contributed to the development of targeted therapies, which focus on specific molecular mechanisms within diseased cells while minimizing damage to healthy cells. This has been particularly evident in cancer treatment, where some drugs are specifically designed to target defined genetic mutations, resulting in improved therapeutic efficacy and reduced side effects compared to conventional chemotherapy. One of the most significant outcomes of these advancements is the emergence of personalized medicine, which is based on an individual’s genetic characteristics to design the most appropriate therapeutic strategy. Studies have shown that genetic variation among individuals significantly influences drug response, prompting the use of genetic testing to determine optimal drug selection and dosing, especially in cardiovascular diseases, cancer, and chronic disorders. This approach represents an important step toward improving healthcare quality and enhancing patient safety. Despite the substantial benefits of genetic engineering, its application raises several ethical and scientific challenges, particularly regarding human gene modification and its potential impact on future generations, as well as concerns related to genetic data privacy and confidentiality, and the high cost of advanced genetic technologies. These challenges necessitate the establishment of clear ethical and regulatory frameworks to ensure responsible and equitable use of such technologies. Conclusion Genetic engineering represents a cornerstone of modern medicine, having driven a true revolution in disease diagnosis and treatment, and steering medical practice toward greater precision and personalization. With continued scientific advancement, genetic engineering applications are expected to expand into broader fields, contributing to improved human health and the development of a more advanced and sustainable medical future. Dr. ASSEEL HASHIM RADHI