Q.Describe the process of ligation in genetic engineering. Which enzyme is used, and what type of chemical bond does it form to join two DNA fragments?

[!TLDR] DNA ligase joins the sticky/blunt ends of the vector and insert by forming covalent phosphodiester bonds, sealing the DNA backbone. …

Once a vector and an insert have been cut with the same (or a compatible) restriction enzyme, mixing them together allows any complementary sticky-end overhangs to find each other and base-pair through hydrogen bonds. This base-pairing, however, only holds the two pieces of DNA loosely and temporarily aligned; it leaves a physical break, or nick, in the sugar-phosphate backbone of each strand at the point where the two fragments meet, because hydrogen bonding between bases does not itself repair the broken backbone. …

Distinguish clearly between the temporary hydrogen-bond alignment of sticky ends and the pe …

Do not say sticky-end base-pairing alone completes the join -- ligase's covalent phosphodiester bond …