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DNA Definition
Deoxyribonucleic acid, or DNA, is a biological macromolecule that carries hereditary information in many organisms. DNA is necessary for the production of proteins, the regulation, metabolism, and reproduction of the cell. Large compressed DNA molecules with associated proteins, called chromatin, are mostly present inside the nucleus. Some cytoplasmic organelles like the mitochondria also contain DNA molecules.DNA is usually a double-stranded polymer of nucleotides, although single-stranded DNA is also known. Nucleotides in DNA are molecules made of deoxyribose sugar, a phosphate and a nitrogenous base. The nitrogenous bases in DNA are of four types – adenine, guanine, thymine and cytosine. The phosphate and the deoxyribose sugars form a backbone-like structure, with the nitrogenous bases extending out like rungs of a ladder. Each sugar molecule is linked through its third and fifth carbon atoms to one phosphate molecule each.
Deoxyribonucleic acid is a molecule composed of two chains that coil around each other to form a double helix carrying the genetic instructions used in the growth, development, functioning, and reproduction of all known organisms and many viruses.