The two polynucleotide chains in DNA are

Options

A. parallel
B. discontinuous
C. antiparallel
D. semiconservative

Explanation

To answer the question, "The two polynucleotide chains in DNA are," we will analyze the options provided and derive the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding DNA Structure**:
- DNA is composed of two polynucleotide chains that form a double helix structure. Each chain is made up of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base.

2. **Identifying the Chains**:
- The two chains in DNA run alongside each other, but they do not run in the same direction. This is a crucial aspect of their structure.

3. **Directionality of the Chains**:
- Each polynucleotide chain has a directionality defined by the orientation of the sugar molecules. One end of the chain is referred to as the 5' end (where the phosphate group is attached), and the other end is the 3' end (where the hydroxyl group is attached).

4. **Antiparallel Orientation**:
- In DNA, one chain runs in the 5' to 3' direction, while the other runs in the opposite direction, from 3' to 5'. This orientation is known as "antiparallel."

5. **Evaluating the Options**:
- **Parallel**: This would mean both chains run in the same direction, which is incorrect for DNA.
- **Discontinuous**: This term relates to DNA replication, not the structure of DNA itself.
- **Antiparallel**: This is the correct description of the orientation of the two chains in DNA.
- **Semi-conservative**: This term also relates to DNA replication, indicating that during replication, one strand is conserved while the other is newly synthesized.

6. **Conclusion**:
- The correct answer is that the two polynucleotide chains in DNA are **antiparallel**.

### Final Answer:
The two polynucleotide chains in DNA are **antiparallel**.