At 5’ end of a polynucleotide chain

Options

A. -OH group is attached
B. Phosphate group is attached
C. Pentose sugar is attached
D. H-bond is present

Answer

To answer the question "At the 5’ end of a polynucleotide chain what do we have?", we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Polynucleotide Chains**:
- A polynucleotide chain refers to a long chain of nucleotides, which are the building blocks of nucleic acids like DNA and RNA.

2. **Components of a Nucleotide**:
- Each nucleotide consists of three components: a phosphate group, a pentose sugar (deoxyribose in DNA), and a nitrogenous base.

3. **Structure of the Polynucleotide Chain**:
- In a DNA molecule, the nucleotides are linked together to form a chain. The sugar and phosphate groups alternate along the backbone of the DNA strand.

4. **Identifying the 5' End**:
- The numbering of the carbon atoms in the sugar molecule is crucial. The 5' carbon of the sugar is where the phosphate group is attached.

5. **Conclusion**:
- Therefore, at the 5' end of a polynucleotide chain, we have a phosphate group attached to the fifth carbon of the sugar molecule.

### Final Answer:
At the 5’ end of a polynucleotide chain, we have a phosphate group.