In order to remain linked the distance between two genes should not increase beyond

Options

A. 10 map units
B. 20 map units
C. 40 map units
D. 50 map units

Answer

To solve the question regarding the distance between two genes for them to remain linked, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Gene Linkage**:
- Gene linkage refers to the tendency of genes that are located close to each other on a chromosome to be inherited together.

2. **Crossing Over**:
- During meiosis, homologous chromosomes can exchange segments in a process called crossing over. This can separate linked genes if the distance between them is too large.

3. **Map Units**:
- The distance between genes is measured in map units (also known as centimorgans). One map unit corresponds to a 1% chance of recombination occurring between two genes.

4. **Determining Maximum Distance for Linkage**:
- For genes to remain linked, the distance between them should not exceed a certain threshold. Generally, if the distance is too great, the likelihood of crossing over increases, which can separate the genes.

5. **Evaluating Options**:
- The options provided are 10 map units, 20 map units, 40 map units, and 50 map units.
- Based on genetic studies, it is understood that genes can remain linked up to about 40 map units. Beyond this distance, the chances of recombination increase significantly.

6. **Conclusion**:
- Therefore, the maximum distance between two genes for them to remain linked is **40 map units**.

### Final Answer:
The distance between two genes should not increase beyond **40 map units** for them to remain linked.

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