The structure of DNA consists of two long strands forming a double helix. Each strand is composed of a backbone made of alternating sugars and phosphate groups, with nitrogenous bases (adenine, thymine, cytosine, and guanine) attached to the sugar. The strands are anti-parallel and held together by complementary base pairing (A-T, C-G). DNA carries genetic information essential for inheritance, cell function, and development, making it a key molecule in all living organisms.