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DNA is a long polymer made up of repeating units called nucleotides. Each nucleotide consists of a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base. The four nitrogenous bases found in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T). The sugar and phosphate molecules make up the backbone of the DNA strand, while the nitrogenous bases project inward from the backbone.
