DNA, or deoxyribonucleic acid, is a molecule that contains the genetic instructions for the development, function, growth, and reproduction of all living organisms. It is composed of four different chemical building blocks called nucleotides, each with a unique nitrogenous base – adenine, thymine, guanine, and cytosine. The arrangement of these bases determines the genetic code of an organism. DNA is found in the nucleus of cells and can also be found in some organelles, like mitochondria. It is responsible for passing down traits from parents to offspring and plays a crucial role in the evolution and diversity of species. Advances in DNA technology have enabled scientists to manipulate and study DNA, leading to many discoveries and applications in various fields such as medicine, agriculture, and forensics.