The presence or absence of a hydroxyl group at which carbon atom of the pentose sugar distinguishes RNA from DNA?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → C-2
The sugar in RNA is β-D-ribose, which has an –OH group at C-2. The sugar in DNA is β-D-2-deoxyribose: “2-deoxy” means the oxygen at C-2 is missing, so C-2 carries H instead of OH. C-1, C-3 and C-4 are the same in both sugars.
NCERT (2026-27 edition):
10.5.1 Chemical Composition of Nucleic Acids – “Complete hydrolysis of DNA (or RNA) yields a pentose sugar, phosphoric acid and nitrogen containing heterocyclic compounds (called bases). In DNA molecules, the sugar moiety is β-D-2-deoxyribose whereas in RNA molecule, it is β-D-ribose.”
