Glycosidic bonds exist in DNA molecule between
(a) Sugar and phosphate
(b) Any two nitrogen bases
(c) Sugar and nitrogen base
(d) Purines and pyrimidines

Options

A. Sugar and phosphate
B. Any two nitrogen bases
C. Sugar and nitrogen base
D. Purines and pyrimidines.

Answer

To determine where glycosidic bonds exist in a DNA molecule, let's analyze the options provided:

1. **Understanding DNA Structure**: DNA is made up of nucleotides, which are the building blocks of DNA. Each nucleotide consists of three components: a sugar (deoxyribose in DNA), a phosphate group, and a nitrogenous base (which can be either a purine or a pyrimidine).

2. **Identifying Glycosidic Bonds**: A glycosidic bond is a type of covalent bond that connects a sugar molecule to another molecule, which in the case of DNA, is the nitrogenous base. Specifically, the glycosidic bond forms between the first carbon of the sugar (deoxyribose) and the nitrogen atom of the nitrogenous base.

3. **Evaluating the Options**:
- **(a) Sugar and phosphate**: This is incorrect. The bond between sugar and phosphate is called a phosphodiester bond, not a glycosidic bond.
- **(b) Any two nitrogen bases**: This is also incorrect. There are hydrogen bonds between nitrogen bases, not glycosidic bonds.
- **(c) Sugar and nitrogen base**: This is correct. The glycosidic bond exists between the sugar (deoxyribose) and the nitrogenous base.
- **(d) Purines and pyrimidines**: This is incorrect. Purines and pyrimidines refer to the types of nitrogenous bases (adenine and guanine are purines; cytosine and thymine are pyrimidines), and they are connected by hydrogen bonds, not glycosidic bonds.

4. **Conclusion**: The correct answer is **(c) Sugar and nitrogen base**.

### Final Answer:
The glycosidic bonds exist in a DNA molecule between **(c) Sugar and nitrogen base**.