question_answer 17)

  'Restriction' in restriction enzyme refers to (a) cleaving of phosphodiesterbonci in DNA by the enzyme (b) cutting of DNA at  specific position only (c) prevention of the multiplication of bacteriophage in bacteria

Answer:

                  (b) The restriction enzymes are called' molecular scissors' and are responsible for cutting DNA. Restriction enzymes belong to a class of enzymes called nucleases. They are of two types (i) Exonucisassscul DNA at the ends (ii) Endonucieases Make cuts at specific positions within the DNA. These enzymes are present in bacteria to provide a type of defense mechanism called the ?restriction modification system?. This system consist of two components, restriction enzyme and modification enzyme, The term 'restriction' refer to the function of these enzyme in restricting the propagation of foreign DNA of bacteriophage in host bacterium, i.e., cutting of DNA, at specific position only.