← Chapter 18 - Recombinant DNA and Biotechnology Export Options Alphabetize Word-Def Delimiter Tab Comma Custom Def-Word Delimiter New Line Semicolon Custom Data Copy and paste the text below. It is read-only. Select All Definition: Restriction enzymes Enzymes used to cut DNA into fragments. Definition: DNA Ligase Enzyme that unites broken DNA strands (Okazaki fragments) during replication and recombination. Definition: Recombinant DNA A DNA molecule made in the laboratory that is derived from two or more genetic sources. Definition: Sticky ends On a piece of two-stranded DNA, short, complementary, one-stranded regions produced by the action of a restriction endonuclease. Sticky ends facilitate the joining of segments of DNA from different sources. What happens after a DNA molecule has been cut with a restriction enzyme? The complementary sticky ends form hydrogen bonds with one another. How did Cohen and Boyer make the first recombinant DNA? They used restriction enzymes to cut sequences from two E. coli plasmids containing different antibiotic resistance genes. Then they used DNA ligase to join the fragments together. The resulting plasmid, when inserted into new E. coli cells, gave those cells resistance to both antibiotics.