In the DNA molecule

Options

A. The total amount of purine nucleotides and pyramidine nucleotides is not always equal
B. There are two strands which run parallel in the `5'rarr3'` direction
C. The proportion of adenine in relation to thymine varies with the organism
D. These are two strands which run antiparallel one in `5'rarr3'` direction and other in `3'rarr 5'`

Answer

### Step-by-Step Solution:

1. **Understanding the Structure of DNA**:
DNA (deoxyribonucleic acid) is composed of two long strands that form a double helix. Each strand is made up of nucleotides, which are the building blocks of DNA.

2. **Identifying the Chains**:
In a DNA molecule, there are two strands. These strands are often referred to as the "backbones" of the DNA.

3. **Directionality of the Strands**:
The two strands of DNA run in opposite directions, which is known as anti-parallel orientation. One strand runs in the 5' to 3' direction, while the other runs in the 3' to 5' direction.

4. **Conclusion**:
Therefore, the key points about the DNA molecule are:
- It consists of two strands.
- The strands run in an anti-parallel fashion.
- One strand runs from 5' to 3', and the other runs from 3' to 5'.

### Final Answer:
In the DNA molecule, there are two strands that run in an anti-parallel direction: one strand runs from 5' to 3', and the other runs from 3' to 5'.

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