Genes A and B are farther apart than are genes A and C, and all three are linked. What CANNOT be concluded?

Options

A. B might be between A and C
B. C might be between A and B
C. A might be between B and C
D. More crossovers will occur between A & B than between A&C

Answer

To solve the question regarding the genetic linkage of genes A, B, and C, we need to analyze the relationships and distances between these genes based on the information provided. Here’s a step-by-step breakdown of the reasoning process:

### Step-by-Step Solution:

1. **Understanding Genetic Linkage**:
- Genes A, B, and C are linked, which means they are located on the same chromosome. The distance between genes affects the likelihood of crossing over occurring between them.

2. **Comparing Distances**:
- It is given that genes A and B are farther apart than genes A and C. This implies that the distance between A and B (d_AB) is greater than the distance between A and C (d_AC).
- Mathematically, this can be expressed as: d_AB > d_AC.

3. **Analyzing Possible Arrangements**:
- We need to evaluate the possible arrangements of genes A, B, and C based on their distances:
- **Option 1**: B might be between A and C.
- **Option 2**: C might be between A and B.
- **Option 3**: A might be between B and C.
- **Option 4**: More crossing over will occur between A and B than between A and C.

4. **Evaluating Each Option**:
- **Option 1**: If B is between A and C, then the distance d_AC would be less than d_AB, which contradicts the given information. Therefore, this option cannot be concluded.
- **Option 2**: If C is between A and B, this arrangement is possible and does not contradict the distance information.
- **Option 3**: If A is between B and C, this could also be possible depending on the distances.
- **Option 4**: Since d_AB > d_AC, it is logical that crossing over would be more frequent between A and B than between A and C.

5. **Conclusion**:
- The only option that cannot be concluded based on the given information is **Option 1**: "B might be between A and C".

### Final Answer:
**Option 1: B might be between A and C cannot be concluded.**

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