The plasmid vector is isolated from bacterial cell and cleaved at one side by restriction ...........

Explanation

**Step-by-Step Solution:**

1. **Understanding Plasmids**: A plasmid is an extrachromosomal, self-replicating circular DNA molecule found in bacteria. It can replicate independently of chromosomal DNA and is often used as a vector in genetic engineering.

2. **Role of Plasmids in Genetic Engineering**: Plasmids are utilized to introduce foreign DNA into a host organism. They serve as vectors to carry the desired DNA fragment that needs to be inserted into the host.

3. **Cleavage by Restriction Enzymes**: To insert the desired DNA into the plasmid, the plasmid must first be cleaved. This is done using restriction endonucleases, which are enzymes that cut DNA at specific sequences.

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