The use of technology to alter the genomes of viruses, bacteria, and other cells for
medical or industrial purposes is called genetic engineering. These days, bacteria,
plants, and animals are genetically engineered to produce biotechnology products.
Organisms that have had a foreign gene inserted into them are called transgenic
organisms. (TRANSferred GENE = TRANS GENIC)
Recombinant DNA technology means to recombine the DNA of an organism to make it
more useful to humans. It is used to produce bacteria that reproduce in large vats to get
them to make a large amount of a particular protein, such as insulin, growth hor-
mone, clotting proteins for hemophiliacs, and hepatitis B vaccine.
Transgenic bacteria can also help plants. For example, bacteria that live in plants have
genes spliced in that let them resist insect toxins; this protects the roots of the plants, too.
Bacteria can be genetically engineered to degrade a particular substance, for instance,
transgenic bacteria have been produced which have the ability to eat oil after an oil
spill. Industry has found that bacteria can he used as filters to prevent airborne chemicals
from being vented into the air. They can also remove sulfur from coal before it is burned
and help clean up toxic dumps. Furthermore, these bacteria were given “suicide” genes
that caused them to self-destruct when the job is accomplished.
Many major mining companies already use bacteria obtain various metals. Genetic
engineering may enhance ability of bacteria to extract copper, uranium, and gold.
Plants can also be genetically engineered to make cotton, corn, soybeans, and potatoes
resistant to pests because their cells now produce an insect toxin.
Plants are also being engineered to produce human hormones, clotting factors, and
antibodies, in their seeds. One type of antibody made by corn can deliver a substance
that kills tumor cells, and another made by soybeans can be used as treatment for genital
Techniques have been developed to insert genes into the eggs of animals. The procedure
has been used to produce larger fish, cows, pigs, rabbits, and sheep. Genetically
engineered fishes are now being kept in ponds that offer no escape to the wild because
there is much concern that they will upset or destroy natural ecosystems.
Gene pharming is the use of transgenic farm animals to produce therapeutic drugs
in the animal’s milk. There are plans to produce drugs for the treatment of cystic
fibrosis, cancer, blood diseases, and other disorders. An anti-clotting medicine is
currently being produced by a herd of goats.
Animals have been engineered to produce growth hormone in their urine instead of in
milk. Urine is preferable to milk because only females produce milk, and not until
maturity, but all animals produce urine from birth.
Scientists have begun the process of genetically engineering animals to serve as organ
donors for humans who need a transplant. We now have the ability to transplant kidneys,
heart, liver, pancreas, lung, and other organs. Unfortunately, however, there are not enough
human donors to go round. Fifty thousand Americans need transplants a year, but only
20,000 patients get them. As many as 4,000 died that year while waiting for an organ.
You might think that apes, such as the chimpanzee or the baboon might be a scientifically
suitable species for this purpose. But apes are slow breeders and many people object to
using apes for this purpose. In contrast, pigs have been an acceptable meat source, and a
female pig can become pregnant at six months and can have two litters a year, each
averaging about ten offspring.
Ordinarily, the human body rejects transplanted pig organs. Genetic engineering,
however, can make pig organs good for transplantation at less of a rejection risk.
Cloning of Animals
Imagine that an animal has been genetically altered to serve as an organ donor. What
would be the best possible way to get identical copies of this animal? If cloning of the
animal was possible, you could get many exact copies of this animal. Cloning is a form
of asexual reproduction (without sex) because it requires only the genes of that one
In 1997, scientists at the Raslin institute in Scotland announced that they produced a
cloned sheep called Dolly. In 1998, genetically altered calves were cloned in the United
States using the same method.
The Human Genome Project
The Human Genome Project was a massive effort to put all of the genes in human
chromosomes into the proper sequence. This was just finished in 2003.
Project goals were to identify all the 25,000 genes in human DNA and determine the
sequences of the 3 billion amino acids that make up human DNA. This allows scientists
to detect some defective genes and tailor a treatment plan to the individual.
Gene therapy gives a patient a normal gene to make up for a faulty gene. For
example, there is a genetic disease of the liver that causes it to malfunction and leads to
high levels of blood cholesterol, which makes the patient subject to fatal heart attacks at a
young age. The person is injected with a virus that contains the normal gene. Another
example is when fat enzymes are coated with the missing gene to cure cystic fibrosis and
then sprayed into patients’ nostrils. Anti-cancer genes can also be injected directly into
cancerous tumors. Perhaps it will be possible also to use gene therapy to cure hemophilia,
diabetes, Parkinson disease, or AIDS.