GENETIC VARIATION AND ITS ROLE IN HEALTH AND PHARMACOLOGY: A NARRATIVE REVIEW
Human genetic variation plays a fundamental role in determining differences among individuals in disease susceptibility, clinical characteristics and responses to medical treatments. Advances in genomic technologies have significantly improved our ability to identify and characterize genetic differences, including single nucleotide variants, insertions and deletions, copy number variations and larger structural changes within the genome. These variations influence biological processes and contribute to both health and disease outcomes, making them essential to the development of precision medicine. This review examines the major forms of human genetic variation and their impact on disease development and pharmacological responses. It explores how genetic variants arise, their distribution across populations, and their involvement in monogenic, oligogenic and polygenic disorders. The review also highlights the importance of gene–environment interactions and epigenetic factors in shaping disease risk and progression. In addition, the paper discusses the growing field of pharmacogenomics, which investigates how genetic differences affect drug metabolism, efficacy and toxicity. Particular attention is given to clinically important variants in drug-metabolizing enzymes, transport proteins, and therapeutic targets that contribute to variability in treatment outcomes among patients. By linking disease genetics with pharmacogenomics, genetic information can be used both to predict disease risk and to guide individualized treatment strategies. Peer Review History: Received 5 April 2026; Reviewed 11 May 2026; Accepted 9 June; Available online 15 July 2026 Academic Editor: Dr. Muhammad Zahid Iqbal, AIMST University, Malaysia, drmmziqbal@gmail.com Reviewers: Dr. Hasniza Zaman Huri, University of Malaya Medical Centre, Kuala Lumpur, hasnizazh@ummc.edu.my Dr. Hayriye Eda Şatana Kara, Gazi University, Turkey, eda@gazi.edu.tr