Plasmids are autonomously replicating mini chromosomes found in :

Options

A. Bacteriophage lambda
B. Leishmania donovani
C. Escherichia coli
D. Paramecium coudatum

Answer

**Step-by-Step Solution:**

1. **Understanding Plasmids:**
- Plasmids are small, circular pieces of DNA that are separate from the chromosomal DNA in bacteria. They can replicate independently within the bacterial cell.

2. **Characteristics of Plasmids:**
- Plasmids are known as "autonomously replicating mini chromosomes" because they can replicate on their own without relying on the bacterial chromosome.
- They often carry genes that provide beneficial traits to the bacteria, such as antibiotic resistance.

3. **Identifying the Organisms:**
- The question provides four options:
A. Bacteriophage lambda
B. Escherichia coli
C. Leishmania donovani
D. Paramecium caudatum

4. **Analyzing Each Option:**
- **A. Bacteriophage lambda:** This is a virus that infects bacteria and does not contain plasmids.
- **B. Escherichia coli:** This is a common bacterium that is known to contain plasmids, which can confer traits like antibiotic resistance.
- **C. Leishmania donovani:** This is a protozoan parasite and does not have plasmids like bacteria do.
- **D. Paramecium caudatum:** This is a unicellular organism (a ciliate) and does not typically contain plasmids.

5. **Conclusion:**
- Among the options, **Escherichia coli** is the organism that contains plasmids, making it the correct answer.

**Final Answer:**
- Plasmids are autonomously replicating mini chromosomes found in **B. Escherichia coli**.

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