Question:
Which of the following is a nucleoside?
Which of the following is a nucleoside?
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Nucleoside = base + sugar, no phosphate; its name often ends in -idine or -osine.
Updated On: Jun 24, 2026
- Adenine
- Uridine
- Thymine
- Guanine
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The Correct Option is B
Solution and Explanation
Step 1: Distinguish the three terms. A base (e.g. adenine) is a nitrogenous ring alone. A nucleoside is a base plus a sugar (ribose or deoxyribose). A nucleotide is a nucleoside plus one or more phosphate groups.
Step 2: Uridine is uracil joined to ribose, so it is a base plus a sugar with no phosphate. That makes uridine a nucleoside, which is the correct answer.
Step 3: Adenine, thymine and guanine are all free nitrogenous bases, not nucleosides, because they lack the attached sugar. Adding ribose would make them adenosine, thymidine and guanosine respectively.
Step 2: Uridine is uracil joined to ribose, so it is a base plus a sugar with no phosphate. That makes uridine a nucleoside, which is the correct answer.
Step 3: Adenine, thymine and guanine are all free nitrogenous bases, not nucleosides, because they lack the attached sugar. Adding ribose would make them adenosine, thymidine and guanosine respectively.
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