Modified (GM) Animals
can not always produce human gene products correctly. Scientists
often need to insert genes into other animals to obtain the
product they need.
animal that contains a gene from another organism is called
a transgenic animal.
leads us neatly back to my beloved oncomice.
These are examples of mice containing human cancer genes.
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.
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.
is exactly the same method used to create the oncomice.
scientists have not stopped at this level. They want to ensure
that inserted genes not only replace faulty genes but also
alter normal genes.
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.
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.
this the right way forward for us?
How far is it to the first cloned human?