The 3'-5' phosphodiester linkages inside a polynucleotide chain serve to join -

Options

A. One DNA strand with the other DNA strand
B. One nucleoside with another nucleoside
C. One nucleotide with another nucleotide
D. One nitrogensou base with pentose sugar

Answer

To answer the question regarding what the 3'-5' phosphodiester linkages inside a polynucleotide chain serve to join, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Polynucleotide Chains**:
- A polynucleotide chain is formed by linking together multiple nucleotides. Each nucleotide consists of three components: a nitrogenous base (adenine, thymine, guanine, cytosine in DNA; uracil in RNA), a sugar molecule (deoxyribose in DNA; ribose in RNA), and a phosphate group.

2. **Identifying the Linkages**:
- The 3'-5' phosphodiester linkages refer to the connections between the phosphate group of one nucleotide and the 3' carbon of the sugar of the next nucleotide. This linkage is crucial for forming the backbone of the polynucleotide chain.

3. **Formation of Phosphodiester Linkages**:
- A phosphodiester bond is formed when the phosphate group of one nucleotide bonds to the hydroxyl group (OH) on the 3' carbon of the sugar of another nucleotide. This creates a continuous sugar-phosphate backbone.

4. **Role of the Backbone**:
- The sugar-phosphate backbone, formed by these phosphodiester linkages, provides structural integrity to the polynucleotide chain. The nitrogenous bases extend from this backbone, allowing for the formation of base pairs in DNA.

5. **Conclusion**:
- Therefore, the 3'-5' phosphodiester linkages serve to join adjacent nucleotides in a polynucleotide chain, creating a stable and structured framework for genetic information.

### Final Answer:
The 3'-5' phosphodiester linkages inside a polynucleotide chain serve to join adjacent nucleotides, forming the sugar-phosphate backbone of the DNA or RNA molecule.