Question

In DNA N-glycosidic linkage is present between:

• A. Pentose sugar and phosphate group
• B. Nitrogenous base and pentose sugar
• C. Two nitrogenous bases
• D. Two pentose sugars

Hint:

Base + sugar forms nucleoside via N-glycosidic bond; adding phosphate forms nucleotide.

Answer 1

The Correct Option is B

Concept: DNA is a polymer made up of repeating units called nucleotides. Each nucleotide consists of three essential components: a nitrogenous base (purine or pyrimidine), a pentose sugar (deoxyribose), and a phosphate group. The stability and structure of DNA depend on specific covalent and non-covalent bonds that link these components together. Among these bonds, the N-glycosidic bond plays a crucial role in forming the fundamental nucleotide structure.

Step 1: Using nucleotide structural composition in DNA.
A nucleotide is formed when a nitrogenous base attaches to a pentose sugar. In DNA, the sugar is deoxyribose, and bases include adenine, guanine, cytosine, and thymine. This base-sugar unit forms the nucleoside before phosphate attachment.

Step 2: Using definition of N-glycosidic bond formation.
The N-glycosidic bond is a covalent linkage formed between the nitrogen atom of the nitrogenous base (N9 in purines and N1 in pyrimidines) and the 1' carbon atom of the pentose sugar. This bond is essential for forming nucleosides.

Step 3: Using differentiation of DNA bonding systems.
DNA structure is stabilized by three major types of bonds: - N-glycosidic bond (base + sugar) - Phosphodiester bond (sugar + phosphate backbone) - Hydrogen bonds (between complementary bases) Thus, each bond has a distinct structural role. Final Understanding: The N-glycosidic bond specifically connects nitrogenous base with pentose sugar, forming the foundation of nucleotide structure.