A mixture containing DNA fragments A,B,C and D, with molecular weights of `A + B = C,A gt B and D gt C`, was subjected to agarose gel electrophoresis. The positions of these fragments from cathode to anode sides of the gel would be

Options

A. B, A, C, D
B. A, B, C, D
C. C, B, A, D
D. B, A, D, C

Answer

To solve the problem of determining the positions of DNA fragments A, B, C, and D after agarose gel electrophoresis, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Given Information**:
- We have four DNA fragments: A, B, C, and D.
- The relationships between their molecular weights are given as:
- \( A + B = C \)
- \( A > B \)
- \( D > C \)

2. **Interpreting the Relationships**:
- From \( A + B = C \), we can infer that both A and B are smaller than C. Therefore, \( A < C \) and \( B < C \).
- Since \( A > B \), we can conclude that \( B < A < C \).
- The relationship \( D > C \) indicates that D is larger than C.

3. **Arranging the Fragments by Size**:
- Now we can summarize the sizes of the fragments:
- \( B < A < C < D \)
- This implies that the order of the fragments from smallest to largest is B, A, C, and D.

4. **Understanding Agarose Gel Electrophoresis**:
- In agarose gel electrophoresis, DNA fragments are separated based on size. Smaller fragments move faster and travel further towards the anode (positive side), while larger fragments move slower and do not travel as far.
- Since we have established the size order as \( B < A < C < D \), the order of their movement from the cathode (negative side) to the anode (positive side) will be the reverse of their size order.

5. **Final Order of Fragments**:
- Therefore, the order from the cathode to the anode will be:
- **B, A, C, D**

### Conclusion:
The correct answer is **BACD**.

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