CBSE Class 12-science Answered

Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites but between the same two bases of the opposite strands. This leaves single-stranded unpaired bases at cut ends so that they form hydrogen bonds with their complementary cut counterparts. These cut ends with unpaired bases are called sticky ends or cohesive ends. The sticky ends facilitate the action of enzyme DNA ligase. DNA ligase connects the Okazaki fragments, closing the gaps between their sugar-phosphate backbones by catalysing the formation of phosphodiester bonds.