The unpaired nucleotides produced by the action of restriction enzymes are referred to as sticky ends.

Here's why:

* Restriction enzymes cut DNA at specific sequences, often leaving short, single-stranded overhangs.

* These overhangs are "sticky" because they can base pair with complementary overhangs on other DNA fragments that have been cut by the same enzyme.

* This ability to form complementary base pairs makes sticky ends crucial for ligation, the process of joining DNA fragments together.

Let me know if you have any other questions!