In a linear chromosome map, distances between 4 loci is as follows, a-b 10%, a-d 3%, b-c 4% and a-c 6%. The cross over frequency between c and d is

Options

A. 0.03
B. 0.09
C. 3 or 9%
D. 4 to 12%

Answer

To find the crossover frequency between loci C and D based on the given distances in a linear chromosome map, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Distances**:
- A to B = 10%
- A to D = 3%
- B to C = 4%
- A to C = 6%

2. **Construct a Genetic Map**:
- Start by placing the loci on a linear map based on the distances provided.
- Place A at the start, then B at 10% from A.
- Place D at 3% from A, which is closer to A than B.
- Place C at 6% from A.

3. **Determine the Position of Loci**:
- From the map, we have:
- A = 0%
- D = 3%
- C = 6%
- B = 10%
- B is the farthest from A, and thus is at the end of the line.

4. **Calculate the Distance Between C and D**:
- The distance between C and D can be calculated by finding the difference in their positions:
- Distance (C to D) = Position of C - Position of D
- Distance (C to D) = 6% - 3% = 3%

5. **Convert to Crossover Frequency**:
- The crossover frequency is equivalent to the distance in centimorgans (cM), which is the same as the percentage distance.
- Therefore, the crossover frequency between C and D is 3%.

### Final Answer:
The crossover frequency between loci C and D is **3%**.

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