Read the following text and answer the question on the basis of the same:
DNA, a long polymer of deoxyribonucleotide. Altmann and these substances to be acidic hence he named nucleic acid. The basic unit of DNA is a nucleotide which has three components a nitrogenous base, a pentose sugar (deoxyribose) and a phosphate group. There are two types of nitrogenous bases in DNA, Purine and Pyrimidine. J. Watson and E. Crick proposed a double helix model for the structure of DNA. There are four types of DNA i.e., A, B, C, Z.
Which DNA form has maximum number of base pairs per turn?
Which among the following does not confer stability to the helical structure of DNA ?

Options

A. Phosphodiester bond
B. H-bond
C. N-glycosidic linakge
D. All of these.

Explanation

### Step-by-Step Solution

1. **Understanding DNA Structure**:
- DNA is a long polymer made up of deoxyribonucleotides. Each nucleotide consists of three components: a nitrogenous base, a pentose sugar (deoxyribose), and a phosphate group.

2. **Types of Nitrogenous Bases**:
- There are two categories of nitrogenous bases in DNA: Purines (which include adenine and guanine) and Pyrimidines (which include cytosine and thymine).

3. **Double Helix Model**:
- J. Watson and E. Crick proposed the double helix model for the structure of DNA. This model describes how two strands of DNA are coiled around each other.

4. **Types of DNA**:
- The text mentions four forms of DNA: A, B, C, and Z. Each form has distinct structural characteristics.

5. **Maximum Base Pairs per Turn**:
- Among the different forms of DNA, Z-DNA has the maximum number of base pairs per turn, which is due to its zigzag structure and a pitch of 3.8 nm.

6. **Stability of DNA Structure**:
- The stability of the helical structure of DNA is conferred by several types of bonds:
- Phosphodiester bonds between nucleotides.
- Hydrogen bonds between nitrogenous bases.
- However, the N-glycosidic linkage (which connects the nitrogenous base to the sugar) does not contribute to the stability of the helical structure.

7. **Conclusion**:
- Therefore, the answer to the question regarding which DNA form has the maximum number of base pairs per turn is Z-DNA.
- The answer to which factor does not confer stability to the helical structure of DNA is the N-glycosidic linkage.