Originally created for DNA Interactive ( www.dnai.org ) TRANSCRIPT A common technique in genetic engineering is to insert a new gene into a loop of bacterial DNA called a plasmid. The molecular tool used to cut DNA is a restriction enzyme such as EcoRI. The enzyme has a precise shape that allows it to run along the groove of the double helix, scanning for the base letter sequence GAATTC EcoRI then cuts the plasmid at this specific point... ...allowing a new piece of DNA to be inserted. When it cuts, EcoRI leaves a sticky end, which helps the new gene to attach. The joins are THEN stitched together by another enzyme called DNA ligase. The genetically engineered bacteria is then grown in a culture medium. Very quickly, large numbers of the bacteria can be produced, each with a copy of the inserted gene. The bacteria duly manufacture whatever protein the gene codes for, and so the desired product is produced.
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