The first recombinant plasmid was constructed from
a) Salmonella typhimurium
b) Acetobacter coli
c) Escherichia coli
d) Agrobacteria tumifaciens

Options

A. Salmonella typhimurmm
B. Acetobacter coli
C. Escherichia coli
D. Agrobacteria tumifaciens

Answer

To answer the question about the first recombinant plasmid constructed, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Recombinant Plasmids**: A recombinant plasmid is a DNA molecule that has been artificially created by combining DNA from different sources. This is a fundamental technique in biotechnology.

2. **Historical Context**: The first successful construction of a recombinant plasmid occurred in 1972 by researchers Cohen and Boyer. They were pioneers in genetic engineering.

3. **Source of the Gene of Interest**: The gene of interest used in the first recombinant plasmid was derived from **Salmonella typhimurium**. Specifically, it was an antibiotic resistance gene that was extracted from the plasmid of this bacterium.

4. **Host for the Plasmid**: The plasmid that was used to create the recombinant DNA was from **Escherichia coli** (E. coli). However, the key point here is that the gene of interest came from **Salmonella typhimurium**.

5. **Conclusion**: Therefore, when asked about the source of the first recombinant plasmid, the correct answer is **Salmonella typhimurium**.

### Final Answer:
The first recombinant plasmid was constructed from **Salmonella typhimurium**.

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