Arrange the following steps in correct sequence which are involved in cloning of recombinant DNA.
(A) Cut the DNA of plasmid and gene of interest by the same restriction enzyme
(B) Join foreign DNA to plasmid by ligase to produce recombinant DNA
(C) Introduction of recombinant DNA in E. coli
(D) Replication and multiplication of recombinant DNA in E. coli
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B), (C), (D)
(A) Cut the DNA of plasmid and gene of interest by the same restriction enzyme — this comes first. The same enzyme leaves the same sticky ends on both pieces, so they can pair with each other.
(B) Join foreign DNA to plasmid by ligase to produce recombinant DNA — this comes second. The sticky ends of the gene pair with those of the cut plasmid, and DNA ligase seals them. The joined molecule is the recombinant DNA. This can be done only after the cutting.
(C) Introduction of recombinant DNA in E. coli — this comes third. The recombinant DNA is put into the host cell, which has been made competent to take up DNA, for example by a heat shock.
(D) Replication and multiplication of recombinant DNA in E. coli — this comes last. Only once the DNA is inside the host can the host copy it again and again, and this gives many copies of the gene.
NCERT Extract:
Processes of Recombinant DNA Technology – …
