Question

A recombinant DNA molecule was created by ligating a gene to a plasmid vector. By mistake, an exonuclease was added to the tube containing the recombinant DNA. How does this affect the next step in the experiment, i.e., bacterial transformation ?

Answer 1

DNA ligase :

Enzyme DNA ligase is used to join two DNA fragments by the formation of phosphodiester bonds. In this case, the ligase enzyme joins the gene of interest to the plasmid vector DNA to form a recombinant DNA.

Transformation :

Transformation is the process by which a bacterial cell takes up DNA from its environment. Transformation of the host bacteria, in this scenario, would help the host to take up the recombinant DNA and form multiple exact copies.

Exonuclease :

Exonuclease is an enzyme which removes nucleotides from the ends of a DNA strand.

Effect of exonuclease on bacterial transformation :

Exonuclease works on the free ends of a DNA fragment. In this experiment, the recombinant DNA molecule is a circular DNA composed of a plasmid vector with the gene of interest incorporated into it. Hence, it has no free ends.
Thus, the presence of exonuclease will not affect the experiment.