The following is true about the first ever articifical rDNA

Options

A. Synthesized from DNA of typhodical bacterium & multiplied in its own cell
B. Synthesized from typhoid bacterium &
C. Synthesized by linking gene of Salmonella into plasmid of E.coil
D. Synthesized by linking gene of E.coil into plasmind of Salmonella

Answer

To answer the question regarding the first ever artificial recombinant DNA (rDNA), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding rDNA**: Recombinant DNA (rDNA) is formed by combining DNA from two different sources. The first artificial rDNA was created in the early 1970s.

2. **Identifying Key Scientists**: The first successful experiment to create rDNA was conducted by Herbert Boyer and Stanley Cohen in 1972.

3. **The Experiment**: In their experiment, they used a native plasmid from the bacterium *Salmonella typhimurium*. A plasmid is a small, circular piece of DNA that can replicate independently of chromosomal DNA.

4. **Process of rDNA Creation**: The scientists cut the plasmid DNA and inserted a gene of interest into it, thereby creating recombinant DNA.

5. **Host Cell for Multiplication**: The rDNA needs to be introduced into a host cell for multiplication. In this case, the plasmid from *Salmonella* was used, but it was typically multiplied in *E. coli* cells, which are commonly used as host cells in genetic engineering.

6. **Evaluating the Options**:
- **Option 1**: "Synthesized from DNA of typical bacterium and multiplied in its own cell." - This is incorrect because the rDNA was not synthesized from a typical bacterium.
- **Option 2**: "Synthesized from typhoid bacterium." - This is correct as *Salmonella typhimurium* is related to typhoid.
- **Option 3**: "Synthesized by linking DNA of Salmonella into plasmid of E. coli." - This is incorrect because the plasmid was originally from *Salmonella*, not *E. coli*.
- **Option 4**: "Synthesized by linking gene of E. coli into plasmid of Salmonella." - This is also incorrect as the gene was inserted into the plasmid from *Salmonella*.

7. **Conclusion**: The correct answer is **Option 2**: "Synthesized from typhoid bacterium."