Question

Two nucleotides are joined together by a linkage known as:

• A. Disulphide linkage
• B. Glycosidic linkage
• C. Phosphodiester linkage
• D. Peptide linkage

Answer 1

The Correct Option is C

To identify the correct bond between two nucleotides, understanding nucleotide composition and nucleic acid formation (DNA/RNA) is necessary.

1. Nucleotide Composition:
   • Each nucleotide comprises three constituents: a sugar, a phosphate group, and a nitrogenous base.
2. Inter-Nucleotide Bonding:
   • Nucleotides are linked sequentially via a bond formed between the phosphate group of one nucleotide and the 3' -OH group of the sugar on the subsequent nucleotide. This establishes a chain with a repeating sugar-phosphate backbone.
   • The specific bond type is termed a phosphodiester linkage. This bond connects the 5' carbon of one sugar to the 3' carbon of the next sugar in the chain through the phosphate group.
   • This phosphodiester linkage is fundamental to the nucleic acid backbone, dictating their structural geometry and function.
3. Exclusion of Alternative Bonds:
   • Disulphide linkage: Primarily observed in protein structures for tertiary and quaternary stabilization; absent in nucleic acids.
   • Glycosidic linkage: Characteristic of carbohydrates, connecting sugars, and forms part of nucleoside structure, but not the inter-nucleotide link.
   • Peptide linkage: Defines protein backbones by joining amino acids; not involved in nucleotide connection.

Therefore, the correct linkage joining two nucleotides is the phosphodiester linkage.