The Role of Genetic Variation in Human Health and Disease

Abstract

Genetic variation refers to differences in DNA sequence among individuals and populations. It is a fundamental feature of human biology and contributes to differences in physical traits, physiological responses, disease susceptibility, and responses to medicines. Genetic variants may include single-nucleotide variants, small insertions and deletions, copy-number changes, structural variants, and changes in regulatory regions. Their effects range from neutral to strongly pathogenic, and many health outcomes reflect interactions among multiple variants and environmental factors. Genome-wide association studies and sequencing technologies have expanded understanding of how common and rare variants contribute to complex diseases. This paper examines nine major aspects of genetic variation, including types of variants, functional effects, inherited disease, complex disease risk, pharmacogenomics, population diversity, gene-environment interaction, genomic technologies, and implications for personalized medicine.