DNA is a polymer made of nucleotides containing deoxyribose sugar, phosphate groups, and one of four nitrogenous bases (A, T, G, C). The nucleotides bond together via phosphodiester linkages between the sugar and phosphate groups to form two anti-parallel polynucleotide chains that intertwine to form the DNA double helix. Hydrogen bonds between A-T and G-C base pairs on opposite strands stabilize the helical structure and allow for the precise copying and transmission of genetic information.