Explain the structure of the DNA double helix, including its subunits and the way in which they are bonded together

DNA is made up of subunits called nucleotides. Each nucleotide is comprised of one nitrogenous base (either adenine, cytosine, guanine, or thymine), one phosphate, and one deoxyribose sugar. The nucleotides are connected by the sugar-phosphate backbone which is a covalent bond while the nitrogenous bases are connected by hydrogen bonds. Adenine connects to thymine, guanine connects to cytosine. The strands are antiparallel meaning they run in opposite directions and form a double helical structure. Include a diagram showing at least four nucleotides and how they're connected.