The human genome contains approximately three billion base pairs of DNA organized into 23 pairs of chromosomes. The Human Genome Project, completed in 2003, provided the first comprehensive map of human genetic material. Genes encode the instructions for building proteins, which carry out most biological functions in cells. Genetic mutations can cause diseases ranging from cystic fibrosis to various forms of cancer. CRISPR-Cas9 technology has revolutionized genetic engineering by allowing precise editing of DNA sequences. Personalized medicine uses genetic information to tailor treatments to individual patients, improving efficacy and reducing side effects.