Four genetic markers on chromosome Ill of Drosophila melanogaster are studied in a series of dihybrid crosses. It is determined that the distances between pairs of loci are `{:("A to B", 5 cm), ( "A to C" , 11 cm), ("B to C", 7 cm), ("B to D", 6 cm):}`
Which one of the following is true

Options

A. The order of loci could be A_B_C_D
B. The order of loci could beA_B_D_C
C. The order of loci could be B_A_D_C
D. The order of loci could be B_A_D_C

Answer

To solve the problem regarding the genetic markers on chromosome III of Drosophila melanogaster, we need to determine the correct order of the loci based on the given distances between them. Here’s a step-by-step breakdown of how to approach this:

### Step 1: List the Distances
We start by listing the distances provided between the genetic markers:
- Distance between A and B: 5 cm
- Distance between A and C: 11 cm
- Distance between B and C: 7 cm
- Distance between B and D: 6 cm

### Step 2: Analyze the Distances
Next, we analyze these distances to understand the relative positions of the genes:
- The maximum distance is between A and C (11 cm), indicating that A and C are the farthest apart.
- The distance between B and C is 7 cm, which is less than the distance between A and C but more than the distance between A and B (5 cm) and B and D (6 cm).

### Step 3: Determine Gene Order
Using the distances, we can infer the order of the genes:
1. Since A and C are the farthest apart, we can place them at the ends.
2. B is closer to both A and C, so it should be placed between A and C.
3. D is only compared with B, and since B and D are 6 cm apart, D can be placed next to B.

From this analysis, we can propose the following order:
- A (5 cm) - B (6 cm) - D (7 cm) - C (11 cm)

### Step 4: Verify the Order
To verify, we check the distances:
- A to B: 5 cm (correct)
- B to C: 7 cm (correct)
- A to C: 11 cm (correct)
- B to D: 6 cm (correct)

### Conclusion
The correct order of the loci based on the distances provided is:
**A - B - D - C**