"sticky ends" allow dna fragments to be spliced into vectors by what type of bonding?

Answer;

Covalent bonds

Explanation;Sticky ends refers to the bases of DNA that are unpaired because of the action of the restriction enzymes. Sticky ends are referred to as sticky because they have complementary bases.  Sticky ends allow base pairing through covalent bonds between the bases.The action of restriction enzymes results to overhangs, or the so called sticky ends which allow perfect base pairing, where Adenine (A) pairs with Thyamine (T) and Guanine (G) pairs with cytosine (C), as a result of covalent bonding.