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DNA (Deoxyribonucleic Acid) is the molecule that carries genetic information in living organisms. It is composed of two strands that form a double helix structure, made up of nucleotides. Each nucleotide consists of a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G). The sequence of these bases encodes the genetic instructions necessary for the development, functioning, and reproduction of all living organisms. DNA is found in the nucleus of eukaryotic cells and the cytoplasm of prokaryotic cells, and it plays a key role in heredity and cellular processes such as protein synthesis.