Genetically Modified Organisms
Genetically modified organisms are organisms with artificially altered DNA.
They can be created by:
a. Adding a foreign gene.
b. Altering the base sequence of an existing
gene.
c. Deleting or "Turning off"
and existing gene.
Adding a Foreign Gene:
Organisms that are altered in this way are known as transgenic
organisms.
A new foreign gene is added from a different species. The new foreign gene
thus produces the protein it is responsible for, either creating a product
we desire, or modifying the transgenic organisms so they can better survive.
Examples of uses of transgenic organisms:
1. Incorporating bacterial genes for resistance to herbicides so a crop
plant is not killled by weed killer (herbicide).
*2. Incorporating bacterial genes which produce
their own insecticide into corn plants. Herbivorous insects are thus prevented
from eating such plants.
3. Some bacteria thrive on toxic waste. The genes allowing breakdown of
the toxic substance can be added to other more numerous bacteria and then
applied to toxic spills for cleanup (bioremediation).
4. Sheep have been modified to carry the gene for alpha-1-antitrypsin.
This protein is produced in the sheep's milk, which is then give to humans
to treat hereditary emphysema!
5. The gene for insulin production has been aded
to yeast. These recombinant yeast thus produce large quantities of insulin
for use by diabetic humans.
Altering an Existing Gene:
Existing genes in the organism are altered to make it produce at higher
levels (such as growth hormone which makes the organism larger). Or gene complexes
in tissues where these complexes usually don't work are switched on to make
the desired protein (the basis of gene therapy).
Deleting/ "Turning Off" an Existing Gene:
Existing genes may be deleted or deactivated to prevent the expression of
their trait (so they don't produce their protein). *An
example involves deactivating the gene responsible for the ripening of tomatoes.
This new gene can then be inserted into tomato DNA to give them a longer shelf
life.
Slichter