Ribose vs deoxyribose: a five-carbon sugar lacking a 2′-hydroxyl group (2′-OH) is found in which nucleic acid? Select the molecule that contains 2′-deoxyribose as its sugar.

Introduction / Context:The key chemical difference between DNA and RNA sugars is the presence or absence of a hydroxyl group at the 2′ carbon. This small change affects stability, structure, and susceptibility to base-catalyzed hydrolysis.

Given Data / Assumptions:

• DNA contains 2′-deoxyribose, which lacks a hydroxyl group at the 2′ position (it has hydrogen instead).
• RNA contains ribose, which bears a 2′-OH group.
• mRNA and tRNA are forms of RNA and thus contain ribose.

Concept / Approach:The absence of the 2′-OH in DNA increases chemical stability, making the phosphodiester backbone resistant to alkaline cleavage compared with RNA, where the 2′-OH can attack the adjacent phosphate. Therefore, the nucleic acid featuring 2′-deoxyribose is DNA.

Step-by-Step Solution:Identify the sugar: 2′-deoxyribose → no 2′-OH → DNA.Exclude RNA subclasses (mRNA, tRNA) which possess ribose with 2′-OH.Note that “rDNA” (recombinant DNA) is still DNA, but the standard, general answer is DNA itself.

Verification / Alternative check:Textbook structures of deoxyribose vs ribose show H vs OH at the 2′ position, aligning with DNA vs RNA.

Why Other Options Are Wrong:RNA (including mRNA and tRNA) carries the 2′-OH and is susceptible to alkaline hydrolysis; “rDNA only” needlessly restricts the correct category, as all DNA uses deoxyribose.

Common Pitfalls:Misreading “lacking a hydroxyl” as “lacking oxygen entirely”; deoxyribose still contains oxygen atoms but not at the 2′ position.

Final Answer:DNA.