Genetic testing

Genetic testing is used in many ways including determining diseases a couple is likely to pass on to an offspring, determining a disease a foetus is likely to have after delivery on the likelihood of the onset of a disease in adulthood.

Testing is also done to match organ donors to recipients, to establish paternity or maternity, and in forensics, for identifying evidence from crime scenes.

Testing can also help diagnose adult-onset inherited diseases, such as Huntington's disease.

Genetic tests are now available for a range of cancers. These tests don't test for cancer directly, but instead indicate an increased likelihood of developing a cancer. Likelihood is far from certainty, and cancer may or may not develop, since it must be triggered by additional mutations.

Meanwhile, many cancers develop in persons without so-called 'cancer genes'. For example, the two gene variants that have been linked with breast cancer, called BRCA1 and BRCA2 are involved in only 5% of breast cancer cases.

The decision to test is loaded as you may rather not know of an incurable disease that would afflict you after 40 years. On the other hand, knowing can help you take decisions as to whether to have children or not.

Making medicines
Not long ago, insulin needed for diabetic patients would have to come from a pig or growth hormones could only be obtained from dead bodies making them very expensive. Now bacteria can be programmed through genetic engineering to produce medicines.

These types of bacteria are known as transgenic bacteria. Plants can also be used similarly such as bananas being programmed to deliver vaccines. More research is ongoing on how genetic engineering can be used to treat other diseases.

New therapies
One would easily ask why faulty genes in humans cannot simply be fixed by inserting 'good' genes. It is not that easy to do as can be imagined.

There are challenges along the whole process. There has been some success with this as far as blood cells are concerned since they can be easily removed, engineered and placed back. Researchers hope however that new cures through the use of stem cells can be obtained for heart disease, cancer, HIV, Parkinson's disease etc.

Stem cell controversy
Human stem cells are very useful in gene therapy research and treatment and there is no problem with this. The debate however is the source of stem cells. Stem cells can be obtained from cord blood, bone marrow, tooth pulp etc. but they are not as versatile as stem cells obtained from human embryo and this is where the debate is. Do we just 'make' human embryos for the sake of research alone and destroy the unwanted ones?

Spare parts from pigs?
Donated human organs such as hearts, lungs, and livers are in short supply so some geneticists are considering 'humanising' pigs for organ donation and already tests are underway in transplanting genetically altered pig organs into monkeys.

Ethics
The new possibilities created by genetics have brought with them new questions about what is right. An example is genetic testing which for now is optional.

What happens when these tests become less and less optional as has happened with many other tests? Who should decide when genetic tests are done and would employers and insurance companies have access to the results?

If prenatal genetic tests become more common, will people with certain genetic traits, diseases, or even predispositions suffer increased discrimination? Will 'designer babies' become the norm? For some, the opportunities presented by genetic testing and therapies smack of eugenics, the use of selective breeding to create 'superior' people.

More broadly, who 'owns' the genetic information or the life-forms that come from research? These questions arise with increasing frequency in industry, where patents are granted for genetically engineered plants and animals, and for genetic sequences.

Companies argue that without patents, they are left with no guarantee that they can recoup their investment when they discover key genes. But do patents stifle progress and the free exchange of ideas, which is so important in science?

Others worry that reckless experimenting will have unforeseen, potentially catastrophic consequences. For example, the prospect of transplanting animal organs into people raises concern that new diseases could jump from animals, as SARS and madcow disease have.

As for gene therapy, some wonder if it's right to tinker with human DNA. Currently, treatments are focused on somatic cells, that is, cells in the body. Any alterations are not passed on to later generations, because DNA in the germ cells that is eggs and sperms are unaffected.

But so-called germ line gene therapy is certainly possible. It could cure diseases before they happened, but might cause other unexpected problems that would persist in later generations.

Food for thought
The genetic modification of plants for food is a hot issue around the world. Genes transplanted to corn, potato, soybean and other food strains can confer desired traits, such as resistance to pests, which lessens the need for toxic pesticides.

Though genetically modified foods are thought to be safe to eat, their impact on the environment may not be fully known yet.