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MCQEasyJEE 2024Nucleic Acids (DNA, RNA)

JEE Chemistry 2024 Question with Solution

Two nucleotides are joined together by a linkage known as:

  • A

    Phosphodiester linkage

  • B

    Glycosidic linkage

  • C

    Disulphide linkage

  • D

    Peptide linkage

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: The question asks the linkage by which two nucleotides are joined.

Find: The correct bond present between adjacent nucleotides in nucleic acids.

A nucleotide contains a sugar, a phosphate group, and a nitrogenous base.

Adjacent nucleotides in DNA or RNA are connected through the phosphate group of one nucleotide and the 3′3'-OH group of the sugar of the next nucleotide, forming a sugar-phosphate backbone.

This bond is called a phosphodiester linkage.

Other options are not correct:

  • Glycosidic linkage is associated with linking sugars or with base-sugar connection in a nucleoside, not the bond between two nucleotides in a nucleic acid chain.
  • Disulphide linkage occurs in proteins between sulfur-containing side chains.
  • Peptide linkage joins amino acids in proteins.

The solution states "The Correct Option is C," but its own explanation concludes phosphodiester linkage, which matches option A in the listed options. Therefore, the correct option is A.

Common mistakes

  • Confusing glycosidic linkage with the bond between nucleotides. Glycosidic linkage connects the nitrogenous base to the sugar, not one nucleotide to the next. Identify the sugar-phosphate backbone bond as phosphodiester linkage instead.

  • Choosing peptide linkage because it is a common biological bond. Peptide linkage belongs to proteins and joins amino acids, so it does not apply to nucleic acids. Match the biomolecule type before selecting the bond.

  • Selecting disulphide linkage from familiarity with structural stabilization. Disulphide bonds are found in proteins involving sulfur-containing amino acids, not in nucleotide chains. Focus on the phosphate involvement in nucleic acids.

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