The length of four DNA fragments P, Q, R and s is such that P is smaller than Q, Q is smaller than 8 and R is greater than S. What would be position of the four given fragments on agarose gel from cathode to anode?

Options

A. R,S,Q,P
B. P,Q,R,S
C. R,Q,S,P
D. Q,P,S,R

Answer

To determine the position of the four DNA fragments (P, Q, R, and S) on an agarose gel from cathode to anode, we need to analyze the given information about their lengths and how they migrate during gel electrophoresis.

### Step-by-Step Solution:

1. **Understand the Length Relationships**:
- We know that:
- P < Q (P is smaller than Q)
- Q < R (Q is smaller than R)
- R > S (R is greater than S)

2. **Establish the Size Order**:
- From the relationships:
- Since P is smaller than Q, we can denote their order as:
- P < Q
- Since Q is smaller than R, we have:
- Q < R
- Since R is greater than S, we can write:
- R > S
- Combining these, we can summarize the relationships as:
- P < Q < R
- S < R

3. **Determine the Relative Sizes**:
- From the above relationships, we can conclude:
- P is the smallest fragment.
- Q is the second smallest.
- S is smaller than R but we do not know its exact position relative to Q.
- R is the largest fragment.

4. **Positioning on Agarose Gel**:
- In gel electrophoresis, smaller DNA fragments migrate faster and travel further towards the anode (positive end), while larger fragments migrate slower and remain closer to the cathode (negative end).
- Given our established order:
- P (smallest) will migrate the furthest.
- Q will be next.
- S will be next.
- R (largest) will migrate the least.

5. **Final Order from Cathode to Anode**:
- Therefore, the order of the fragments from cathode to anode is:
- R (closest to cathode)
- S
- Q
- P (furthest from cathode)

### Final Answer:
The order of the fragments from cathode to anode is: **R, S, Q, P**.