aqa science © nelson thornes ltd 2006 1 b1b 6.5 genetic engineering genetic engineering remember:...

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.



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



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



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



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



Bacteria multiply rapidly and produce many millions of copies of themselves, all able to make insulin using the

incorporated insulin gene.

Genetic engineering



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


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



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



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



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.


aqa science © nelson thornes ltd 2006 1 b1b 6.5 genetic engineering genetic engineering remember:...

Documents

genetic engineering

genetic engineering

hormone insulin slide

human insulin

sufficient insulin

incorporated insulin

dna glue slide

plasmid sticky ends