<p>Recombinant DNA (rDNA) technology has revolutionised modern medicine by providing precise genetic manipulation for therapeutic, diagnostic, and preventive uses. By integrating genetic material from multiple sources, rDNA permits the creation of physiologically active compounds and the development of new medical therapies. This study summarises the basics of rDNA technology, including DNA separation, gene cloning, vector design, transformation, and expression systems, emphasising their foundational importance in biotechnology. Recombinant procedures make it possible to produce insulin, growth hormones, interferons, monoclonal antibodies, and enzymes on a large scale with better purity, safety, and scalability in the biopharmaceutical industry. Subunit, DNA, and viral-vector vaccines are examples of recombinant vaccines that have been effectively used to prevent infectious diseases such COVID-19, HPV, and hepatitis B. Gene therapy techniques using viral and non-viral vectors, together with CRISPR-based genome editing, provide targeted repair of genetic diseases. Additionally, recombinant systems promote pharmacogenomics and personalised medicine by improving molecular diagnostics such as PCR, qPCR, DNA probes, and enzyme-based tests. Furthermore, platforms for translational research and disease modelling are provided by genetically modified animal and cell models. The paper further examines ethical, safety, and regulatory considerations, as well as upcoming technologies such as CRISPR 2.0, synthetic biology, mRNA therapies, and designer vaccinations. Together, rDNA technology is still revolutionising healthcare by providing novel approaches to illness diagnosis, treatment, and prevention.</p> Graphical Abstract <p></p>