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Biomolecules question

2005 · Shift 0 · Q23
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Biomolecules question

2005 · Shift 0 · Q23

JEE MainChemistryBiomoleculesMCQ+4 / −1
In both DNA and RNA, heterocyclic base and phosphate ester linkages are at-
  1. A
    C5′C_5^{'}C5′​ and C2′C_2^{'}C2′​ respectively of the sugar molecule
  2. B
    C2′C_2^{'}C2′​ and C5′C_5^{'}C5′​ respectively of the sugar molecule
  3. C
    C1′C_1^{'}C1′​ and C5′C_5^{'}C5′​ respectively of the sugar molecule
  4. D
    C5′C_5^{'}C5′​ and C1′C_1^{'}C1′​ respectively of the sugar molecule
View written solutionFree

Correct answer: C

  1. Identify the bonding positions in nucleotides

    In both DNA and RNA, each nucleotide has:

    • a nitrogenous base attached to the sugar,
    • a phosphate group attached to the sugar.

  2. Position of heterocyclic base attachment

    The nitrogenous base is linked to the pentose sugar through a β\betaβ-N-glycosidic bond at the C1′C_1'C1′​ carbon of the sugar.

  3. Position of phosphate ester linkage

    The phosphate group is attached to the C5′C_5'C5′​ carbon of the sugar. In nucleic acids, phosphodiester linkages connect the 3′3'3′-OH of one sugar to the 5′5'5′-phosphate of the next, but the phosphate is characteristically attached at C5′C_5'C5′​ of the nucleotide sugar.

  4. Match with the options

    Therefore:

    • heterocyclic base linkage →C1′\to C_1'→C1′​
    • phosphate ester linkage →C5′\to C_5'→C5′​

    This corresponds to:

    Option C: C1′C_1'C1′​ and C5′C_5'C5′​ respectively of the sugar molecule

  5. Final answer

    C\boxed{\text{C}}C​

  6. Comparison with stored correct answer

    Stored correct answer = C

    My derived answer = C

    Hence, they agree.

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