What is the nature of the strands of the DNA duplex?

Options

A. Anti-parallel and complementary
B. Identical and complementary
C. Anti-parallel and non-complementary
D. Dissimilar and non-complementary

Answer

### Step-by-Step Solution:

1. **Understanding DNA Duplex**:
- A DNA duplex consists of two strands that coil around each other to form a double helix.

2. **Nature of the Strands**:
- The strands of the DNA duplex are described as **complementary**. This means that the sequence of bases on one strand determines the sequence of bases on the other strand. For example, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).

3. **Polarity of Strands**:
- Each strand of DNA has a directionality, often referred to as polarity. One strand runs in the 5' to 3' direction, while the other runs in the 3' to 5' direction. This opposite orientation is crucial for the complementary nature of the strands.

4. **Anti-parallel Orientation**:
- The strands are also described as **anti-parallel**. This means that while one strand runs from the 5' end to the 3' end, the other strand runs from the 3' end to the 5' end. This anti-parallel arrangement is essential for the proper base pairing between the strands.

5. **Conclusion**:
- Therefore, the nature of the strands of the DNA duplex is that they are **complementary** and **anti-parallel**.

### Final Answer:
The nature of the strands of the DNA duplex is that they are **complementary and anti-parallel**.

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