Adjacent nucleotides in a polynucleotide chain are joined by

Options

A. N-glycosidic bond
B. Phosphodiester bond
C. O-glycosidic bond
D. Hydrogen bond

Answer

To answer the question about how adjacent nucleotides in a polynucleotide chain are joined, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Nucleotides**:
- A nucleotide is composed of three components: a nitrogenous base, a pentose sugar (which can be ribose in RNA or deoxyribose in DNA), and a phosphate group.

2. **Identifying Bonds in Nucleotides**:
- The nitrogenous base is attached to the pentose sugar via a bond known as a **glycosidic bond**.
- The phosphate group is connected to the pentose sugar through a bond called an **ester bond**.

3. **Formation of Polynucleotide Chains**:
- When nucleotides link together to form a polynucleotide chain, the phosphate group of one nucleotide connects to the sugar of the next nucleotide. This linkage is established through a **phosphodiester bond**.

4. **Role of Hydrogen Bonds**:
- It is also important to note that hydrogen bonds form between the nitrogenous bases of complementary nucleotides (e.g., between adenine and thymine, or guanine and cytosine in DNA), but these do not connect adjacent nucleotides in the chain.

5. **Conclusion**:
- Therefore, the correct answer to the question is that adjacent nucleotides in a polynucleotide chain are joined by **phosphodiester bonds**.

### Final Answer:
Adjacent nucleotides in a polynucleotide chain are joined by **phosphodiester bonds**.

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