Read the following passage and answer the questions that follow :
We know that plasmids and bacteriophages are the most commonly used vectors in biotechnology experiments. If we can link an alien piece of DNA to the plasmid DNA, the alien DNA can be multiplied equal to the copy number of the plasmid. Engineered vectors are used these days. Study the diagram of the E. coli cloning vector pBR322 and answer the questions that follow :
(c) Name the two restriction sites each in the two genes you have identified as selectable markers.
Show Hint
Pst I and Pvu I lie in ampR; Bam HI and Sal I lie in tetR.
Step 1: Recall the two marker genes:
The selectable markers of pBR322 are ampR and tetR.
Each has its own set of restriction sites where alien DNA can be inserted.
Step 2: Sites in ampR:
The ampR gene carries the sites Pst I and Pvu I.
Step 3: Sites in tetR:
The tetR gene carries the sites Bam HI and Sal I.
Insertion of alien DNA at one of these sites inactivates that gene, which helps identify recombinants.
Final Answer:
ampR: Pst I and Pvu I. tetR: Bam HI and Sal I.
