JEE Main · 2005 · 08 May 2005 · Offline · Biomolecules

In both DNA and RNA, heterocyclic base and phosphate ester linkages are at-

(A) $C_{5}^{1}$ and $C_{2}^{1}$ respectively of the sugar molecule
(B) $C_{2}^{⊥}$ and $C_{5}^{⊥}$ respectively of the sugar molecule
(C) $C_{1}^{'}$ and $C_{5}^{'}$ respectively of the sugar molecule✓ Correct
(D) $C_{5}^{⊥}$ and $C_{1}^{⊥}$ respectively of the sugar molecule

Answer: (C)

Solution

In a nucleotide the two attachment points on the pentose sugar are fixed. The nitrogenous base hangs from the

C_{1}^{'}

carbon through an

N

-glycosidic bond, while the phosphate group is esterified at the

C_{5}^{'}

carbon. These same positions hold in both DNA and RNA, the phosphate then linking the

5^{'}

carbon of one sugar to the

3^{'}

carbon of the next along the backbone.

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

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