The two strands/two polynucleotide chains of DNA are

Options

A. similar I nature and antiparallel
B. discontinuous in nature
C. antiparallel and complementary
D. parallel and discontinuous

Answer

To answer the question regarding the nature of the two strands or two polynucleotide chains of DNA, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding DNA Structure**:
- DNA is composed of two strands that form a double helix. Each strand is a polynucleotide chain made up of nucleotides.

2. **Base Pairing**:
- The two strands are held together by complementary base pairing. This means that specific bases pair with each other: adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).

3. **Directionality of Strands**:
- The strands of DNA have directionality. One strand runs in the 3' to 5' direction, while the other runs in the 5' to 3' direction. This opposite orientation is referred to as being "anti-parallel."

4. **Nature of the Strands**:
- The two strands are not similar in nature; they are complementary. This means that the sequence of bases on one strand determines the sequence of bases on the other strand.

5. **Evaluating the Options**:
- **Option A**: Similar in nature and anti-parallel - Incorrect, as the strands are not similar.
- **Option B**: Discontinuous in nature - Incorrect, as the strands are continuous.
- **Option C**: Anti-parallel and complementary - Correct, as the strands are indeed anti-parallel and complementary.
- **Option D**: Parallel and discontinuous - Incorrect, as the strands are anti-parallel and continuous.

6. **Conclusion**:
- The correct answer is **Option C**: The two strands or two polynucleotide chains of DNA are anti-parallel and complementary.