Question

Following steps are involved in cloning a eukaryotic gene in a bacterial plasmid vector.
I. Introduction of cloning vector into cells.
II. Insertion of eukaryotic DNA into the vector.
III. Identification of cell clones that carry the inserted eukaryotic gene.
IV. Isolation of the vector and the eukaryotic gene-source DNA.
V. Cloning of cells (and foreign DNA).
Select the correct sequence of cloning method.

• A. I - II - III - IV - V
• B. V - IV - III - II - I
• C. III - V - II - IV - I
• D. IV - II - I - V - III
• E. II - IV - I - III - V

Answer 1

The correct option is D IV - II - I - V - III

In order to get multiple copies of a gene, that particular DNA region has to be isolated from the source and joined into a DNA vector which has the ability to replicate itself. DNA cloning involves these steps:

1) A piece of DNA is isolated or cut from the source DNA with the help of restriction enzymes.

2) The vector is also simultaneously digested by the same restriction enzymes to creat the same sites where this foreign DNA can be aligned.

3) The foreign DNA is pasted into a vector with the help of enzyme called DNA ligase.

4) This foreign DNA when ligated into DNA vector is introduced into a host cell, or the bacterium or yeast by a process of transformation. Bacterial cells transform this foreign DNA along with their own DNA resulting in multiple copies of the cloned DNA