Scientists are applying genetic technologies in many areas of life - with the potential for major change, writes Dick Ahlstrom, Science Editor.
GENTICALLY ENGINEERED FOODS:
Scientists use genetic engineering to bring new characteristics to crops and other plants. "Foreign" genes from bacteria, plant species or humans can be inserted in a plant's genome, allowing the plant to produce a foreign substance. The bacteria, Bacillus thuringiensis, produces a natural insecticide and the gene that does this has been inserted in corn and potato varieties. These modified plants produce the insecticide, which kills attacking insects without the need for sprayed insecticides.
Herbicide-tolerant soyabeans and beets are produced by inserting another bacterial gene into them, allowing them to survive chemical sprays that kill surrounding weeds.
Researchers and the companies involved herald these developments as a way to improve agriculture. Opponents claim there are hidden risks and say not enough is known about how these modified plants might spread traits to others nearby.
DRUGS AND GENE THERAPY: In 1981 the human gene that produces insulin was inserted in the genome of a yeast, allowing the organism to produce pure, human insulin for diabetics. Vital insulin supplies formerly came from animal sources. Many drugs including penicillin are now produced by genetically engineered yeast and bacteria that carry inserted foreign genes.
Gene therapy is an attempt to treat inherited diseases by replacing the faulty gene responsible for the disease. The idea is to use a carrier and insertion system such as a harmless virus to bring the replacement gene into cells where it can produce the missing substance associated with the disease.
Researchers use "naked DNA" to insert working elements of DNA which begin to function in the recipient. It is being tested in the treatment of the AIDS virus, and in rheumatoid arthritis. It is also under study in the treatment of cancers.
DISEASE SCREENING: As researchers continue studying the human genome, our genetic blueprint, they are discovering more and more genes responsible for certain diseases. By studying the genetic make-up of prospective parents it is possible to identify the likelihood that any offspring will have an inherited disorder. It is also possible to screen for genetic diseases by taking a cell sample from a developing embryo.
Determining who should have access to this information represents a huge ethical issue. Knowing a person's chance of developing an inherited disease later in life may affect employment prospects, access to bank services or insurance cover. Yet knowing the risk would help prospective parents make informed choices about having children.
This knowledge also helps doctors provide the best treatments for patients with inherited disorders and can give absolute confirmation for the cause of symptoms.
GENETIC FINGERPRINTING: In 1984 Sir Alec Jeffreys developed a method for linking a DNA sample to its genetic source. The technique, DNA or genetic fingerprinting,has become an essential forensic tool that has helped to solve crime but also to protect the innocent. It relies on being able to look for matching DNA sequences, information that for example can prove or disprove the parentage of a child.
It most cases it provides an accuracy of identification in the tens to hundreds of millions to one. Its use has trapped perpetrators but has also exonerated the innocent who might otherwise have been found guilty due to circumstantial evidence.
DNA fingerprinting also has applications in food safety. A Dublin company, IdentiGEN, uses it to track down the source of meat products. A steak on a supermarket shelf can be traced back to the farm and the individual animal that supplied the meat. The company also has tests to identify modified plant products.
STEM CELLS: Stem cells are undifferentiated master cells that can grow into any type of tissue. Researchers believe they hold great promise in new medical treatments for degenerative diseases including Parkinson's and Alzheimer's. The idea is to insert them near a source of damage and the stem cells will then change into and replace damaged cells. Embryos are a rich source of stem cells but their use is ethically contentious. Abortion clinics have been a key source of embryonic stem cells for research purposes.
The farming of embryos for research is also difficult to accept.
The use of stem cells to treat disease looks so promising, however, that researchers are searching for stem cells from other sources. The discarded umbilical cord is a good source and researchers are finding stem cells in adult tissues.
Treatments that might follow include the repair of spinal damage and reversal of progressive blindness.
CLONING AND DESIGNER BABIES: Cloning is one of the most contentious areas of genetic research. Reproductive cloning is illegal in many countries and most scientists reject its use, but cloning can be used to produce embryonic stem cells which have great value in research. The notion of cloning to produce replacement body parts is fallacious because if a human clone could be produced it would be a fully functioning person, not an automaton.
The idea of producing "designer babies" is also repugnant to most people. We may soon identify genes associated with height, hair and eye colour, intelligence, longevity and personality. Should parents be allowed to choose the characteristics that will be passed on to their children?
Animal cloning will continue to be important to researchers. The death in February last of six-year-old Dolly the cloned sheep remains disquieting however, because she died young and had suffered early onset arthritis.
