Sugar identity in nucleic acids: Fill in the blanks—The pentose sugar in RNA is _____, whereas the pentose sugar in DNA is _____.

Introduction / Context:
The identity of the pentose sugar differentiates RNA and DNA chemistry, influencing stability, susceptibility to hydrolysis, and structural conformations like A-form vs B-form helices.

Given Data / Assumptions:

• RNA contains a 2'-hydroxyl group on ribose; DNA lacks it (deoxyribose).
• Options include sugars and unrelated moieties (phosphate, uracil).
• We match RNA → ribose; DNA → deoxyribose.

Concept / Approach:
Ribose has OH at the 2' position, enabling greater reactivity and promoting A-form helices in RNA. Deoxyribose lacks this OH, aiding DNA’s chemical stability and preference for B-form under physiological conditions.

Step-by-Step Solution:
Identify RNA sugar: ribose.Identify DNA sugar: 2'-deoxyribose.Select the option “ribose, deoxyribose.”

Verification / Alternative check:
Chemical hydrolysis of RNA under alkaline conditions is facilitated by the 2'-OH; DNA is resistant—consistent with ribose vs deoxyribose.

Why Other Options Are Wrong:

• Deoxyribose first is reversed.
• Phosphate and uracil are not sugars.

Common Pitfalls:
Confusing the sugar difference (ribose vs deoxyribose) with base difference (uracil vs thymine).

Final Answer:
ribose, deoxyribose