Explain how modified plasmids are made by genetic engineering and how the use of markers enable bacteria containing these plasmids to be detected.

- Isolate wanted gene using restriction enzymes to get DNA and produce sticky ends - Use ligase to join wanted gene to plasmid - Also include marker gene e.g. antibiotic resistance - Add plasmid to bacteria to grow (colonies) then (replica) plate onto medium where the marker gene is expressed - Bacteria not killed have antibiotic resistance gene and (probably) the wanted gene