Multiple choice

What is the effect of insertion of the DNA fragment into pBR322 using restriction enzyme Pst I or Pvu I?

pBR322 is the most widely used plasmid of 4362bp. Its entire sequence is known. It has a replication module of E.coli plasmid, Col E1.This module has been incorporated in many other plasmid vectors since it permits plasmid replication even when chromsome replication and cell division are inhibited by aminoacid starvation or chloramphenicol. It has two selectable markers( tetracycline, tetR  and ampicillin, ampR resistant genes) and only single or unique recognition sites for 12 different restriction enzymes.

  1. The recombinant vector will be resistant to tetracycline but sensitive to ampicillin.

  2. The recombinant vector will be resistant to ampicillin but sensitive to tetracycline.

  3. The recombinant vector will be resistant to both ampicillin and tetracycline.

  4. The recombinant vector will be sensitive to both ampicillin and tetracycline.

  5. None of these
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A Correct answer
Explanation

Unique restriction site for restriction enzymes PstI and PvuI IS located within the ampR gene. So, the DNA fragment inserted within the ampR  gene makes it nonfunctional. Bacterial cells containing such recombinant pBR 322 will be unable to grow in the presence of ampicillin but shall be resistant to tetracycline.

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