Question

Which of the following is not included as a step in cloning in bacteriophage PI?

(a) The growth of vector is done as a plasmid by using pBR322 origin of replication

(b) Cleaving with BamH1 is done and then products cleaved with Sau3A are ligated

(c) Incubation with mutant lysogen is done which doesn’t cleaves the recombinants at pac sites

(d) Incubation is done with mutant lysogen which doesn’t contains head and tail proteins

I have been asked this question in an internship interview.

The origin of the question is Bacteriophage-Mu and Bacteriophage-Pi in section Other Vector Systems for E of Genetic Engineering

Answer 1

The correct choice is (c) Incubation with mutant lysogen is done which doesn’t cleaves the recombinants at pac sites

For explanation: Bacteriophage PI is a complex vector. The growth of vector is done as a plasmid by using pBR322 origin of replication. Cleaving with Bam H1 is done and it is followed by ligation with Sau3A partial digestion products. It is followed by incubation with mutant lysogen which cleaves the recombinants at pac sites but there are no head and tail proteins. It is followed by incubation in lysogen in which cleavage is not carried out at pac sites but there are head and tail proteins. It leads to packaging into heads.