Which sugar is found in DNA?

• A. Deoxyribose sugar
• B. Ribose sugar
• C. Glucose
• D. Fructose

Answer: (A)

DNA uses a five-carbon sugar called deoxyribose. The name reflects that it is missing one oxygen compared with the sugar in RNA—specifically, the 2' carbon has only a hydrogen instead of an OH group. This small difference makes the DNA backbone more chemically stable, which helps DNA store genetic information reliably. In the DNA backbone, deoxyribose links with phosphate groups to form phosphodiester bonds, connecting the 3' end of one sugar to the 5' end of the next, while the bases attach to the 1' carbon of the sugar. In contrast, RNA uses ribose, which has a hydroxyl group at the 2' position, making RNA more reactive and less stable. Glucose and fructose are hexose sugars used mainly for energy metabolism and are not components of nucleic acids.