Question

7. Describe the importance and action of restriction enzymes.

Answer 1

Restriction enzymes are the enzymes which cut DNA at a specific location called as restriction site. They are present naturally in bacteria as a mechanism of Defence against viruses. As soon as viral DNA enter the bacterial cell, it is recognised by restriction enzymes and cut off at restriction sites. This leads to complete degradation of viral DNA and thereby protect the bacterial cell from getting virus infection. The bacterial DNA is itself protected from degradation by restriction enzymes by methylating restriction site.

Restriction enzymes are very specific for the restriction sites. Even a presence of a single chemical group like methyl, phosphate or acetyl or any other or even a single base pairs change renders restriction enzymes to recognise the site.

Restriction enzymes are very useful in molecular cloning and are commonly called as molecular scissors. They are used for cutting plasmid DNA and obtaining gene of interest from given piece of DNA. They are also used to generate restriction map of chromosomes.

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