Biology · Principles and Processes in Biotechnology

What causes restriction enzymes to produce overhanging single-stranded stretches called 'sticky ends' on DNA strands?

1. They cut both strands exactly at the center of the palindrome site, leaving blunt ends
2. They cut the strand a little away from the centre of the palindrome sites between the same two bases on the opposite strands
3. Exonucleases digest the entire length of DNA except the recognition sequence
4. DNA ligase removes terminal phosphates to expose reactive hydroxyl groups