DNA is the fundamental code of life and the central biological archive of all living organisms. This remarkably complex and precisely structured molecule stores the genetic instructions that govern cellular processes , development, growth, adaptation, and reproduction. Present in nearly every cell of the human body, DNA orchestrates the formation of tissues and organs, regulates metabolic pathways , and influences physical traits such as height, pigmentation, and body composition, while also shaping immune function , disease susceptibility , and aspects of cognition and behavior. Beyond defining individual characteristics, DNA acts as a dynamic and continuously evolving record of human evolutionary history . Variations in genetic sequences reflect millions of years of adaptation to changing environments, shifting climates, emerging pathogens, and evolving lifestyles. These inherited differences help explain why populations respond differently to environmental ...