AQA Science © Nelson Thornes Ltd B1b 6.5 Genetic engineering Genetic engineering Remember: In addition to their nucleoid (main chromosome)bacteria have additional small circular pieces of genetic material in their cells called plasmids.

B1b 6.5 Genetic engineering AQA Science © Nelson Thornes Ltd Remind me about genes again A human cell nucleus contains 46 chromosomes. These chromosomes are made from DNA. Along the length of the chromosome are genes. One of these genes codes for the hormone insulin

B1b 6.5 Genetic engineering AQA Science © Nelson Thornes Ltd It took decades of research to find out which chromosome contained the insulin gene and where the insulin gene was in that chromosome. Finally the insulin gene was cut out of the chromosome using a restriction enzyme that leaves “sticky ends” Genetic engineering Sticky ends

B1b 6.5 Genetic engineering AQA Science © Nelson Thornes Ltd Genetic engineering First the bacterium was cut open using lysozyme enzyme Then the same restriction enzyme that was used to remove the insulin gene is used to cut into the plasmid leaving matching sticky ends First the bacterium is cut open using lysozyme enzyme and the plasmid is removed plasmid Sticky ends

B1b 6.5 Genetic engineering AQA Science © Nelson Thornes Ltd Genetic engineering The sticky ends on the insulin gene and the plasmid DNA are matched up and joined using another enzyme called Ligase. Ligase is rather like DNA glue

B1b 6.5 Genetic engineering AQA Science © Nelson Thornes Ltd Bacteria multiply rapidly and produce many millions of copies of themselves, all able to make insulin using the incorporated insulin gene. Genetic engineering

B1b 6.5 Genetic engineering AQA Science © Nelson Thornes Ltd The insulin producing bacteria can be grown in large batches. They secrete the insulin into the liquid medium that they grow in. The liquid is collected and purified to produce sufficient insulin for all diabetics. Genetic engineering

B1b 6.5 Genetic engineering Engineered v Pig Insulin Engineered is better because it : Is identical to Human insulin Is faster acting Is less likely to cause immune reactions Is less likely to transmit diseases Can be produced fast enough to match demand Has fewer ethical and religious objectors AQA Science © Nelson Thornes Ltd

B1b 6.5 Genetic engineering Insulin v pancreas transplant Advantages of injecting insulin Readily available to all diabetics Relatively inexpensive short term Disadvantages Only a treatment not permanent Blood sugar requires constant monitoring Diet needs constant control Some patients find it difficult to inject themselves Expensive over life of patient AQA Science © Nelson Thornes Ltd

B1b 6.5 Genetic engineering Insulin v pancreas transplant Advantages of pancreas transplant Permanent cure No more injections No more diet control Disadvantages Risk associated with surgery Expensive one off treatment Need immunosuppresant (anti-rejection) drugs Immunosuppresants may lower immunity to infectious disease AQA Science © Nelson Thornes Ltd

B1b 6.5 Genetic engineering Possible new treatment Stem cells It may be possible in future to take stored stem cells from a person and encourage them to differentiate into the Islets of Langerhans of the pancreas (insulin and glucagon producing cells) This would mean the person would not need anti rejection drugs after the operation as the cells would be his own. AQA Science © Nelson Thornes Ltd