Final answer:
DNA is composed of nucleotides, each consisting of a phosphate group, a sugar (deoxyribose), and a nitrogenous base (A, T, G, or C). The nucleotides form a sugar-phosphate backbone with bases that pair complementarily (A with T and C with G) to create the double helical structure of DNA.
Step-by-step explanation:
Each deoxyribonucleic acid (DNA) molecule is composed of repeating units called nucleotides. Nucleotides have three components: a phosphate group, a five-carbon sugar called deoxyribose, and a nitrogenous base. The nitrogenous bases are the four types of molecules that code the genetic information: adenine (A), thymine (T), guanine (G), and cytosine (C).
The sugar of one nucleotide is connected to the phosphate group of another nucleotide, forming the sugar-phosphate backbone of the DNA. These nucleotides bond together via complementary base pairing, where A pairs with T via two hydrogen bonds, and C pairs with G via three hydrogen bonds, to form the structure of the double helix.