Restriction enzymes Are found in bacteria and are used to cut up DNA from a virus that might enter and take over the bacteria. They cut at specific sequences and leave exposed bases called “sticky ends.” This allows DNA from to sources to be put together.

EcoRIEcoRI digestion produces "sticky" ends, EcoRI

rDNA Methods 1.Remove the plasmid from a bacterial cell. 2.Remove the “gene of interest” from the DNA of donor, i.e. gene for insulin. 3.Cut out the gene of interest using a restriction enzyme. 4.Cut the plasmid with the same restriction enzyme so they will both have the same sticky ends.

5. Put the “gene of interest” or donor gene in the plasmid and seal with DNA ligase. DNA ligase creates the phosphodiester bonds. 6. Put the plasmid back into the bacterial cell. 7. The bacterial cell now has a gene it did not have before. It is called a transgenic organism. The plasmid is called rDNA or recombinant DNA because it has DNA from two sources.