Genetically Modified (GM) Animals

Bacteria can not always produce human gene products correctly. Scientists often need to insert genes into other animals to obtain the product they need.

An animal that contains a gene from another organism is called a transgenic animal.

This leads us neatly back to my beloved oncomice. These are examples of mice containing human cancer genes.

The most common animals used for transgenic techniques are mice or sheep. The required gene, for example a clotting protein needed by haemophiliacs, is inserted into a sheep's chromosomal DNA after fertilisation of the females egg.

Pregnant females have their early zygotes removed, inserted and fused with the human gene in a plasmid using a micro-injection and then the whole thing is reinserted into the female sheep. The selected gene will now be expressed by some of the offspring in their milk and this can be given to haemophiliac sufferers.

This is exactly the same method used to create the oncomice.

However, scientists have not stopped at this level. They want to ensure that inserted genes not only replace faulty genes but also alter normal genes.

They want to have complete control. To be able to overexpress some genes by inserting promoter sequences in front of them for commercial gain. They want to switch some genes on and off at their will.

They also want to ensure that if an organism does contain the gene they want they can clone this to produce several identical animals. This is why they now remove eggs from sheep and insert the genes they want into the eggs and then allow these to grow into identical clones in surrogate mothers. This is how Dolly the sheep was created.

Is this the right way forward for us?

How far is it to the first cloned human?