DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development, functioning, and reproduction of nearly all living organisms. It is structured as a double helix, like a twisted ladder, made of two long strands of repeated units called nucleotides. These nucleotides contain a sugar, a phosphate, and one of four chemical bases: adenine (A), guanine (G), cytosine (C), or thymine (T). The sequence of these bases forms the genetic code that directs the creation of proteins and determines an organism's traits. DNA is organized into chromosomes, and it is inherited from parents to offspring, passing down genetic information through generations.