S-Cool Revision Summary

S-Cool Revision Summary


Human insulin is a protein, normally produced by the b cells of the islets of Langerhans in the pancreas.

Insulin is involved in the regulation of blood sugar levels, but in Diabetes (diabetes mellitus) there is a deficiency in the production of this essential hormone.

Factor VIII

Haemophiliacs suffer from a defective gene that fails to produce Factor VIII, an important agent involved in blood clotting.

Gene therapy is the deliberate 'repair' or replacement of damaged genes. Success has been limited to somatic (body) cells rather than sex cells (gametes). This means that any changes are not passed on to subsequent generations (inherited). The modification of germ line cells (germ line therapy) is likely to be discouraged on moral grounds.

In an example, called severe combined immunodeficiency disease (SCID) the gene for making an enzyme (adenosine deaminase, ADA) is defective and this prevents the immune system from defending the body against infections.

The missing ADA gene is extracted from healthy bone marrow tissue. The gene is then inserted into a virus, which is then rendered harmless (non invasive) by removing its reproductive genes.

Rennet (rennin or rennilase) and cheese making:

Back in the 1960's, the world faced a severe shortage of calf rennet.

Rennet is a protease enzyme added to milk, along with certain bacteria, which coagulate milk proteins, producing the curds. This then separates from the liquid, whey. The semi-solid curds are then treated by adding salt and then matured in containers to make the cheddar-style cheeses.

(Rennet is an enzyme found in the stomachs of young mammals, like calves, and is important in the digestion of milk proteins.)

Public debate of aspects of GE has resulted in arousing great concern for health and the environment. GE is a new technology, and as such is met with scepticism on one hand and enthusiasm on the other. To fully appreciate the advantages and disadvantages, a good understanding of the facts is essential.

Traditional breeding

Traditional crop and animal breeding has been practiced for thousands of years.

Traditional breeding involves selecting animals or plants with particular characteristics and producing individuals that clearly demonstrate the desired trait or characteristic. Crossing takes place, usually between individuals of the same or closely related species.

The gene pool for such improvements, therefore, is limited to those genes found naturally in the breeding individuals.

These include terms such as genetic manipulation, recombinant DNA technology and gene therapy (in humans).

Transplanting foreign tissue carried great risk of rejection by the body's immune system. The patient faces the rest of their life with a cocktail of anti-suppressant drugs.

There is a great shortage in organs suitable for transplantation, resulting in may patients suffering or even dying before they get a chance to have the transplant operation.


Organs from other animals can be used in human transplantation, but they pose a potentially greater risk of rejection.