Which of the following does not confer stability to the helical structure of DNA ?
(a) Phosphodiester bond
(b) H-bond
(c) N-glycosidic linkage
(d) More than one option is correct.

Options

A. Phosphodiester bond
B. H-bond
C. N-glycosidic linkage
D. More than one option is correct.

Answer

To determine which of the following does not confer stability to the helical structure of DNA, we need to analyze each option provided:

1. **Phosphodiester bond (Option a)**:
- The phosphodiester bond is crucial for forming the backbone of the DNA molecule. It connects the 5' phosphate group of one nucleotide to the 3' hydroxyl group of another nucleotide. This bond is essential for maintaining the integrity and stability of the DNA structure. Therefore, this option does confer stability to the helical structure.

2. **Hydrogen bond (Option b)**:
- Hydrogen bonds are formed between complementary nitrogenous bases (adenine with thymine, and guanine with cytosine) on opposite strands of the DNA double helix. These bonds help hold the two strands together and contribute significantly to the stability of the helical structure. Hence, this option also confers stability.

3. **N-glycosidic linkage (Option c)**:
- The N-glycosidic linkage connects the nitrogenous base to the deoxyribose sugar in a nucleotide. While it is important for the formation of nucleotides, it does not play a direct role in stabilizing the helical structure of DNA. Therefore, this option does not confer stability to the helical structure.

4. **More than one option is correct (Option d)**:
- Since we have identified that both the phosphodiester bond and hydrogen bonds confer stability, and the N-glycosidic linkage does not, this option is not correct.

Based on the analysis, the correct answer is **(c) N-glycosidic linkage**, as it does not confer stability to the helical structure of DNA.

### Summary of the Solution:
- **Correct Answer**: (c) N-glycosidic linkage