(a) Mention the difference in the mode of action of exonuclease and endonuclease.
(b) How does restriction endonuclease function? (2)
(a) Exonuclease remove nucleotides from the ends of the DNA whereas endonuclease make cuts at a specific position within the DNA.
(b) Restriction endonuclease recognises and cuts specific palindromic nucleotide sequences in the DNA. These enzymes cut the strand of DNA a little away from the centre of the palindrome sites but between the two bases of the opposite strands. (2)