Arrange the following steps in recombinant DNA technology on the basis of their sequence of Occurrence:
(A) Isolation of desired DNA fragments
(B) Culturing the host cells
(C) Extraction of desired product
(D) Ligation of DNA fragment into vector
(E) Transferring of recombinant DNA to host
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (D), (E), (B), (C)
(A) Isolation of desired DNA fragments — first. The DNA is taken out of the cell in pure form and cut with restriction enzymes to give the fragment that carries the gene of interest.
(D) Ligation of DNA fragment into vector — second. The vector is cut with the same restriction enzyme, so the sticky ends match. DNA ligase then joins the fragment into the vector, giving recombinant DNA.
(E) Transferring of recombinant DNA to host — third. The recombinant DNA is put into competent host cells, for example by treating bacteria with calcium ions and giving a heat shock.
(B) Culturing the host cells — fourth. The host cells that took up the DNA are grown on a large scale, often in bioreactors, so that the gene makes its product.
(C) Extraction of desired product — last. The product is separated and purified (downstream processing) before it is ready for use.
NCERT Extract:
Processes of Recombinant DNA Technology – “Recombinant DNA technology involves several steps in specific sequence such as isolation of DNA, fragmentation of DNA by restriction endonucleases, isolation of a desired DNA fragment, ligation of the DNA fragment into a vector, transferring the recombinant DNA into the host, culturing the host cells in a medium at large scale and extraction of the desired product. Let us examine each of these steps in some details.”