Explain diagrammatically the action of restriction enzyme on DNA.

Explanation

Restriction enzymes cut the DNA strand a little away from the centre of the palindrome sites (these are DNA sequences which are read the same on the two strands, in 5. `rarr` 3. direction as well as 3. - 5. direction), but between the same two bases on the opposite strands leaving single-stranded portions at the ends.
The overhanging stretches thus produced on each strand are called sticky ends. These are named so becuase they form hydrogen bonds with their complementary cut counterparts. The stickiness of the ends facilitates the action of the enzyme DNA ligase.
Restriction endonucleases are used in genetic engineering to form recombinant molecules of DNA, comprising of DNA from different sources/genomes. These sticky ends are complementary to each other when cut by the same restriction enzyme, therefore they can be joined together (end-to-end) using the enzyme DNA ligase
Some restriction enzymes create blunt ends, in which both the strands of DNA are cut at the same site.