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  4. If a desired gene segment is inserted at the SalI restriction site in pBR322 plasmid, the resulting plasmid will confer resistance to

Q. If a desired gene segment is inserted at the SalI restriction site in pBR322 plasmid, the resulting plasmid will confer resistance to

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Solution:

Plasmid pBR322 contains two resistance genes, namely, ampicillin resistance (ampR) and tetracycline resistance (tetR) genes. These resistance genes are used as selectable markers. Besides, this plasmid has a variety of unique restriction recognition or restriction sites for restriction endonucleases.
Two unique restriction sites each for PstI and PvuI are located within the ampR gene, whereas those for BamHI and SalI are located within the tetR gene.
Insertion of a DNA fragment into the plasmid using enzyme PstI or PvuI places the DNA insert within the gene ampR, making ampR non-functional. Bacterial cells containing this recombinant pBR322 will be unable to grow in the presence of ampicillin but will grow in the presence of tetracycline.
Insertion of a DNA fragment into the plasmid using enzyme BamHI and SalI places the DNA insert within the gene tetR, making tetR non-functional. Bacterial cells containing such recombinant pBR322 will not be able to grow in the presence of tetracycline but will grow in the presence of ampicillin.
Solution