Question

Which of the following is not a use of restriction enzymes?

A. Bacteria produce them to cut up foreign viral DNA

B. Making recombinant DNA
C. Cutting a vector when cloning a gene

D. Replicating DNA during PCR

Answer 1

The correct option is D i.e., Replicating DNA during PCR

Rest all options are correct for restriction enzymes.

It’s thought that restriction enzymes evolved as a defense mechanism, allowing bacteria to chop up potentially harmful foreign DNA (e.g., DNA from bacteria-infecting viruses).

The ability of restriction enzymes to reproducibly cut DNA at specific sequences has led to the widespread use of these tools in many molecular genetics techniques. Restriction enzymes can be used to map DNA fragments or genomes. Mapping means determining the order of the restriction enzyme sites in the genome. These maps form a foundation for much other genetic analysis.

The most important use of restriction enzymes has been in the generation of recombinant DNA molecules, which are DNAs that consist of genes or DNA fragments from two different organisms. Typically, bacterial DNA in the form of a plasmid (a small, circular DNA molecule) is joined to another piece of DNA (a gene) from another organism of interest. Restriction enzymes are used at several points in this process. They are used to digest the DNA from the experimental organism, in order to prepare the DNA for cloning. Then a bacterial plasmid or bacterial virus is digested with an enzyme that yields compatible ends. These compatible ends could be blunt (no overhang), or have complementary overhanging sequences. DNA from the experimental organism is mixed with DNA from the plasmid or virus, and the DNAs are joined with an enzyme called DNA ligase.