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 hormone, 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 herpes.
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 animal.
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.