If map distance between genes P and Q is 4 units, between P and R is 11 units, and between Q and R is 7 units, the order of genes on the linkage map can be traced as follows

Options

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Answer

To determine the order of genes P, Q, and R based on the given map distances, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Distances**:
- Distance between P and Q = 4 units
- Distance between P and R = 11 units
- Distance between Q and R = 7 units

2. **Determine the Most Distant Genes**:
- The largest distance is between P and R (11 units). This suggests that P and R are the farthest apart on the linkage map.

3. **Positioning the Genes**:
- Since P and R are the most distant, we can place them at the ends of our linkage map. Let's place P on the left and R on the right:
```
P ----------- R
```

4. **Placing Gene Q**:
- Now, we need to determine where to place Q. We know:
- The distance between P and Q is 4 units.
- The distance between Q and R is 7 units.
- Since the total distance from P to R is 11 units, we can check the placement of Q:
- If Q is placed between P and R, then the distance from P to Q (4 units) plus the distance from Q to R (7 units) should equal the distance from P to R (11 units).
- This works out as follows:
- Distance P to Q = 4 units
- Distance Q to R = 7 units
- Total distance P to R = 4 + 7 = 11 units

5. **Final Order of Genes**:
- Therefore, the order of the genes on the linkage map is:
```
P -- 4 units -- Q -- 7 units -- R
```

### Conclusion:
The correct order of the genes based on the distances provided is P, Q, R.