Plasmid is important because

Options

A. it is required for cell activity
B. it is a highly coiled, condensed DNA
C. it carries a fertility gene
D. it is attached to the circular DNA of bacteria

Answer

**Step-by-Step Solution:**

1. **Understanding Plasmids**: Plasmids are small, circular DNA molecules found in bacteria. They are separate from the bacterial chromosome, which is the main genetic material of the bacterium.

2. **Identifying the Role of Plasmids**: Plasmids play a significant role in the genetic diversity of bacteria. They can carry genes that provide advantages, such as antibiotic resistance or the ability to metabolize certain substances.

3. **Evaluating the Options**:
- **Option A**: "It is required for cell activity." - While plasmids can carry genes that may be beneficial, they are not essential for basic cell activity.
- **Option B**: "It is a highly coiled condensed DNA." - This describes chromosomes, not plasmids. Plasmids are not highly condensed like chromosomes.
- **Option C**: "It carries a fertility gene." - Some plasmids do carry fertility genes, but this is not the primary importance of all plasmids.
- **Option D**: "It is attached to the circular DNA of bacteria." - This option accurately describes the relationship between plasmids and the bacterial chromosome.

4. **Conclusion**: After evaluating all the options, the most accurate statement regarding the importance of plasmids is that they are attached to the circular DNA of bacteria, making **Option D** the correct answer.

**Final Answer**: D. It is attached to the circular DNA of bacteria.

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