A scientist performed the gene mapping experiments in maize. He mapped the gene on chromosomes on the basis of `%` crossing over between different genes. One map unit corresponds to one `%` crossing over or recombination. Te genes showing more than `50%` recombination were not supposed to be linked on same chromosome. In crossing over studies on maize, scientist observed the following `%` crossing over between A B, C, d- between. A and D `10%` between A and C `3%` between genes C and D `7%` between genes A and B `5%` , and between genes C and B `8%` on the basis of above observation find out the correct sequence of tenes Alt B, C, and D on chromosomes :-

Options

A. ACDB
B. ABCD
C. BACD
D. DACB

Answer

To determine the correct sequence of genes A, B, C, and D on a chromosome based on the given percentage of crossing over, we can follow these steps:

### Step-by-Step Solution:

1. **List the Given Percentages of Crossing Over:**
- A and B: 5%
- A and C: 3%
- A and D: 10%
- B and C: 8%
- C and D: 7%

2. **Identify the Closest Genes:**
- The smallest percentage of crossing over indicates the closest proximity of genes. Here, A and C have the smallest percentage of crossing over at 3%. Therefore, A and C are closest to each other.

3. **Determine the Next Closest Gene:**
- The next smallest percentage is A and B at 5%. So, B is the next closest to A.

4. **Positioning the Genes:**
- Based on the above observations, we can place A and C together, and then B next to A:
- A - C (3% apart)
- A - B (5% apart)

5. **Incorporate the Remaining Gene (D):**
- The next closest gene to A is D, which is 10% away. Since A is already connected to C and B, we can place D at the end:
- A - C - B - D
- However, we need to check the distance between C and D, which is 7%. This indicates that D should be placed after C to maintain the correct distances.

6. **Final Arrangement:**
- Based on the distances, the correct order of the genes on the chromosome is:
- B - A - C - D
- This arrangement satisfies all the given crossing over percentages.

### Final Gene Sequence:
**B - A - C - D**