In DNA, which sugar forms the backbone?

In DNA, which sugar forms the backbone?

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

Answer: (C)

The backbone of DNA is built from deoxyribose sugars linked by phosphodiester bonds. Each nucleotide contributes a deoxyribose sugar, and the phosphate group of one nucleotide bonds to the 3′ carbon of one sugar and the 5′ carbon of the next, forming a repeating sugar–phosphate chain. Deoxyribose differs from ribose by lacking an oxygen at the 2′ position (it has a hydrogen there instead of a hydroxyl), which makes DNA more chemically stable and better suited for long-term genetic storage. In contrast, RNA uses ribose as its sugar, which has a 2′-OH group and supports a more reactive, typically single-stranded molecule. Glucose and fructose are not components of nucleic acid backbones; they are energy-supply monosaccharides used in metabolism. So the sugar forming the DNA backbone is deoxyribose.

The backbone of DNA is built from deoxyribose sugars linked by phosphodiester bonds. Each nucleotide contributes a deoxyribose sugar, and the phosphate group of one nucleotide bonds to the 3′ carbon of one sugar and the 5′ carbon of the next, forming a repeating sugar–phosphate chain. Deoxyribose differs from ribose by lacking an oxygen at the 2′ position (it has a hydrogen there instead of a hydroxyl), which makes DNA more chemically stable and better suited for long-term genetic storage. In contrast, RNA uses ribose as its sugar, which has a 2′-OH group and supports a more reactive, typically single-stranded molecule. Glucose and fructose are not components of nucleic acid backbones; they are energy-supply monosaccharides used in metabolism. So the sugar forming the DNA backbone is deoxyribose.