Tricky business

When you carry a gene mutation that supposedly is involved in a serious disease, would you want to know that? Most people will impulsively say “yes”. But if you think it through the answer isn’t so straightforward. Such knowledge could radically change your life. And what for? Carrying the gene variation doesn’t necessarily mean you will actually get the disease. So, read on and think again!

Genetic testing, whole genome sequencing, everything about genes has taken center stage in medical research. But the first thing to realise is that of more than ninety percent of the genes in the humane genome we still don’t know what their function is. Scientists all over the world search frantically for the answers to the questions about which gene does what. But to put it bluntly: so far, we know hardly anything.

Via DNA profiling, individuals can be identified by characteristics of their DNA. (© Alila Medical Media)

Via DNA profiling, individuals can be identified by characteristics of their DNA. (© Alila Medical Media)

Yes, we have produced a listing of the entire human genetic code. But that is in fact nothing more than writing down an extensive series of letters, about three billion pairs. If you can’t read those letters it will have no meaning to you. Well, we can read them, but the meaning of what is written is still outside of our grasp.

Step by step – and those are very, very small steps -, we are discovering mutations in certain genes that seem to be involved in certain diseases. But hardly any rock-hard facts yet. We are far from having a clear, big picture of which gene mutations are causing which disease. And the question is whether we will ever get such a picture since there’s so much interaction and the processes at work are very complicated. Let alone that environmental influences are for a large part responsible for whether or not these genes will be activated and indeed start the disease process.

Testing
But although we don’t know much yet about the significance of all our about 20,000 genes, we have advanced tremendously in the field of genetic testing. Methods to unravel a person’s DNA have become very sophisticated. Testing is a lot faster nowadays and also much more affordable.

A series of different genetic tests exist. The best-known is the DNA test that can determine whether two people are related to one another. This is used for instance when someone is trying to find his or her biological father or mother. DNA profiling, as this type of testing is called, is also employed in court, for example to find out whether the semen found came from the suspect in a sex crime.

In this type of genetic tests, laboratory assistants only study the DNA molecule as it has been taken from a person concerned and compare this with the other DNA molecule involved. Although about 99,9 percent of human DNA sequences are the same in every person, there’s still enough difference to distinguish one individual from the other.

Although about 99,9 percent of human DNA sequences are the same in every person, there’s still enough difference to distinguish one individual from the other. (© Yuri Arcurs - Fotolia.com)

Although about 99,9 percent of human DNA sequences are the same in every person, there’s still enough difference to distinguish one individual from the other. (© Yuri Arcurs – Fotolia.com)

Other kinds of genetic screening focus on finding abnormalities in chromosomes, genes, or proteins. They search for genetic mutations, mainly for medical purposes. To perform the tests, a sample of blood, hair, skin, amniotic fluid, or other tissue can be used. The most famous sample is the buccal smear, produced via a mouth swab.

Lately, a growing number of direct-to-consumer genetic tests have come onto the market. They are for sale at the chemist’s without involvement of a doctor. Certain tests will look for breast cancer mutations, others for mutations linked to cystic fibrosis. There is a lot of controversy surrounding these types of tests. The test results can easily be misread with all its consequences.

“Based on your DNA, we’ll provide specific health recommendations for you”, advertises one of the producers of an over-the-counter genetic test. Apart from the doubt about the accuracy of such tests, even more concerns exist about the following health advice since it is still poorly understood how DNA variations actually may lead to certain diseases. Then there’s less harm in a DNA test promising a dietary advice based on your genes. It is only a waste of money.

Huntington’s
In exceptional cases, it may be useful to know whether you carry a certain genetic mutation. A very clear case of such a hereditary disease is Huntington’s disease, an incurable disorder that damages parts of the brain, affects muscle coordination and leads to cognitive decline. Huntington’s disease is caused by just one defective gene. When father or mother carries this faulty gene, children have a fifty percent chance to also get the disease by the time they’re adults, mostly between 35 and 45 years of age.

It turns out only a small percentage of people from families with Huntington’s cases want to undergo genetic screening. Knowing that in about twenty years’ time you will succumb to a disease with a terrible degenerating course, while you are still in perfect health at the moment, is a burden almost impossible to bear. Persons in that situation often choose a fairly normal life in the healthy years ahead, although in the background the dark threat of the disease constantly looms.

A potential negative effect of genetic testing may be genetic discrimination. Companies that look to hire someone may stop the procedure when a genetic test of the candidate has shown certain defects. Insurance companies may refuse to cover a potential customer carrying some defective genes that appear to be involved in the development of for instance cancer. And you yourself may forget to enjoy life if you are afraid to possibly get certain diseases that may be connected to some abnormalities in your genome.

Even for genetics specialists it is hard to see the wood for the trees where whole genome sequencing is concerned. (© freshidea - Fotolia.com)

Even for genetics specialists it is hard to see the wood for the trees where whole genome sequencing is concerned. (© freshidea – Fotolia.com)

The newest hype is prenatal whole genome sequencing. For about one thousand US dollars, parents can have the complete genome of their still unborn baby written out for them. They end up with a massive amount of information – describing all the gene variations – most of which even the best-informed scientists don’t know what it means. This will create huge anxiety in the expecting parents. It may influence the way in which they will raise their child. And what about the child? Don’t we all have the “right not to know” and shouldn’t we all be allowed to personally make the choice whether we want to know or not?

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Hereditary baldness © Imaginis – Fotolia.com

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