Question

'Restriction' in restriction enzyme refers to

• A. cleaving of phosphodiester bond-in $DNA$ by the enzyme
• B. cutting of $DNA$ at specific position only
• C. prevention of the multiplication of bacteriophage in bacteria
• D. all of the above

Answer 1

Answer: (C)

A restriction enzyme is an enzyme that cuts $DNA$ at or near a specific recognition nucleotide sequences known as restriction sites. These enzymes are found in bacteria and provide a defense mechanism against invading virus. Inside a prokaryote, the restriction enzyme cuts up foreign $DNA$ in a process called 'restriction' while host $DNA$ is protected by a modification enzyme that modifies the prokaryotic $DNA$ and blocks cleavage. Together, these processes form restriction modification system.