If genetic engineering is defined as changing an organism's DNA to
make it more beneficial, genetic engineering has been going on for a very,
very long time in the form of selective breeding. However, actually
going into a cell and changing its genome by
inserting or removing DNA is a very new technology.
Ancient History
Selective breeding has been going on for countless generations. In
fact, it is even mentioned in the Bible (Genesis 30:25 - 43). In the
account, Jacob was employed as a shepherd under his father-in-law Laban.
Instead of receiving wages, Jacob received the black, streaked, and
spotted sheep, and Laban kept all the white sheep. Jacob craftily
arranged for his black sheep to mate with Laban's white sheep, producing
streaked and spotted sheep. Jacob did so well with this scheme that
Laban's family began to get mad at Jacob, and he eventually had to leave.
Difficulties
Selective breeding is effective enough if the
goal is to maintain or gradually improve a group of animals. Over
the decades, selective breeding has brought us improved strains of cattle
and specialized breeds of dogs. However, these advances have taken
hundreds of years to effect. In addition to the time concerns, it is
often impossible to know which traits will be transferred to the
offspring.
Limits
Selective breeding is a long, tedious process that has its limits.
It is impossible through selective breeding to mix traits from two totally
different species. If a junkyard owner wanted a guard dog that could
squirt ink like an octopus, he would be unable to create such an animal.
It is physically impossible, because the genetics of life are such that
traits from two different organisms cannot be mixed. That is where
genetic engineering comes in.
The Progress
Modern genetic engineering began in 1973 when Herbert Boyer and Stanley
Cohen used enzymes to cut a bacteria plasmid
and insert another strand of DNA in the gap. Both bits of DNA were
from the same type of bacteria, but this milestone, the invention of
recombinant DNA technology, offered a window into the previously
impossible -- the mixing of traits between totally dissimilar organisms.
To prove that this was possible, Cohen and Boyer used the same process to
put a bit of frog DNA into a bacteria.
Since 1973, this technology has been made more controllable by the
discovery of new enzymes to cut the DNA differently and by mapping the
genetic code of different organisms. Now that we have a better idea
of what part of the genetic code does what, we have been able to make
bacteria that produce human insulin for diabetics (previously came from
livestock), as well as EPO for people on kidney dialysis (previously came
from urine of people in third world countries with ringworm).
In 1990, a young child with an extremely poor immune system recieved
genetic therapy. Some of her white blood cells were genetically
manipulated and re-introduced into her bloodstream while she watched
Sesame Street. These new cells have taken over for the original,
weak white cells, and her immune system now works properly. Although
relatively few people have had their cells genetically altered, these
advances have made the prospect of mainstream genetic medicine seem more
likely.
The Promise
Genetic engineers hope that with enough knowledge and experimentation, it
will be possible in the future to create "made-to-order"
organisms. This will lead to new innovations, possibly including
custom bacteria to clean up chemical spills, or fruit trees that bear
different kinds of fruit in different seasons. Any trait occurring
in nature can theoretically be mixed with any other to form a totally new
organism that would not otherwise occur in nature.
Current Status
As of late summer of 1998, scientists are able to add simple traits to
organisms. They cannot create custom-made animals. They cannot
always predict how traits will interact. Before phenomenally new
advances can be made, scientists have to learn how to affect cells' DNA
with pin-point accuracy, without affecting other traits. Advances
like genetic correction for nearsightedness are a long way off. The
power of science is limited to knowledge about genetics, gene locations,
and trait interactions, but as knowledge grows, so will scientists'
abilities to manipulate life. |