This document discusses tools and techniques of recombinant DNA technology, including restriction enzymes and gel electrophoresis. Restriction enzymes are naturally found in bacteria where they help the bacteria defend against bacteriophages by cutting the viral DNA. These enzymes cut DNA at specific palindromic sequences. Gel electrophoresis is used to separate DNA fragments by size as fragments will migrate through an agarose gel at different rates in an electric field based on their size. Fragments can then be visualized under UV light after staining with ethidium bromide.