aqa science © nelson thornes ltd 2006 1 b1b 6.5 genetic engineering genetic engineering remember:...
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AQA Science © Nelson Thornes Ltd 2006 1
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
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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
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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
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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
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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
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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
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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
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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
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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
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B1b 6.5 Genetic engineering
Possible new treatment Stem cellsIt 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.
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