Find the odd one out, with respect to Chargaff's rule.

Options

A. `A+T= C+G`
B. `A+G = C+T `
C. `(A+G)/(C+T)=1`
D. Base ratio A/T is close to unity and C/G is also close to unity

Answer

To solve the question of finding the odd one out with respect to Chargaff's rule, we need to understand the principles of Chargaff's rule and analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Chargaff's Rule**:
Chargaff's rule states that in DNA, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal to the amount of cytosine (C). This can be summarized as:
- A = T
- G = C
- Therefore, the total amount of purines (A + G) equals the total amount of pyrimidines (C + T).

2. **Analyzing the Options**:
Let's look at the options given:
- **Option 1**: A + T = C + G
- **Option 2**: A + G = C + T
- **Option 3**: (A + G) / (C + T) = 1
- **Option 4**: Base ratio A/T is close to unity and C/G is also close to unity.

3. **Evaluating Each Option**:
- **Option 1 (A + T = C + G)**: This does not hold true according to Chargaff's rule. While A = T and G = C, there is no direct equivalence between A + T and C + G.
- **Option 2 (A + G = C + T)**: This is correct as it aligns with Chargaff's rule since purines equal pyrimidines.
- **Option 3 ((A + G) / (C + T) = 1)**: This is also correct because it reflects the equality of purines and pyrimidines.
- **Option 4 (Base ratio A/T is close to unity and C/G is also close to unity)**: This is correct as well, indicating that the ratios of A to T and C to G are approximately equal.

4. **Identifying the Odd One Out**:
Based on the evaluations:
- **Option 1 (A + T = C + G)** is the only statement that does not conform to Chargaff's rule and is therefore the odd one out.

### Conclusion:
The odd one out with respect to Chargaff's rule is **Option 1: A + T = C + G**.