In a DNA molecule, nitrogenous base is linked to pentose sugar by 'A' linkage and the pentose sugar is linked to phosphate by 'B' linkage. Correctly identify A and B.

Options

A. `{:("Column A ","Column B"),("N - Glycoside linkage","Amide linkage"):}`
B. `{:("Column A ","Column B"),("N - Glycoside linkage","Phosphodiester linkage"):}`
C. `{:("Column A ","Column B"),("Phosphodiester linkage","Phosphodiester linkage"):}`
D. `{:("Column A ","Column B"),("Amide linkage","Phosphodiester linkage"):}`

Answer

To solve the question regarding the linkages in a DNA molecule, we need to identify the types of bonds that connect the nitrogenous base to the pentose sugar and the pentose sugar to the phosphate group.

### Step-by-Step Solution

1. **Understanding the Structure of DNA**:
- DNA is made up of nucleotides, which consist of a nitrogenous base, a pentose sugar (deoxyribose), and a phosphate group.

2. **Identifying the Linkage between Nitrogenous Base and Pentose Sugar**:
- The nitrogenous base is attached to the first carbon of the pentose sugar. The type of bond that forms between the nitrogenous base and the sugar is known as a **glycosidic bond**. This bond is formed through a condensation reaction where a water molecule is removed.

3. **Identifying the Linkage between Pentose Sugar and Phosphate Group**:
- The phosphate group is attached to the fifth carbon of the pentose sugar. The bond that forms between the sugar and the phosphate group is called a **phosphodiester bond**. This bond is formed between the hydroxyl group of the sugar and the phosphate group, also through a condensation reaction.

4. **Conclusion**:
- Therefore, we can conclude that:
- **A (linkage between nitrogenous base and pentose sugar)** is **glycosidic linkage**.
- **B (linkage between pentose sugar and phosphate)** is **phosphodiester linkage**.

### Final Answer:
- A = Glycosidic linkage
- B = Phosphodiester linkage