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Predict the future with genetic testing?
Healthy people sometimes become seriously ill. Others who do not care about their health live almost without symptoms. An explanation for this can be found in part in our genome. So what sense does genetic testing make?
Angelina Jolie sparked new interest The breast cancer risk gene BRCA-1 was discovered in actress Angelina Jolie through a genetic test. Molecular geneticists extracted the DNA from their cells and "read" the genetic information stored there. Because of the increased risk of developing ovarian or breast cancer, Jolie had both breasts amputated and, with this announcement, triggered a wave of worldwide interest in genetic diagnosis. Prophylactic breast amputations are questionable and only make sense for very few women, according to the American Cancer Society (ACS).
Only a dozen genetic diseases can be treated with gene therapy Each person carries the innate properties on two 23, 46 chromosomes, which are located in the nuclei of the body cells. Around 25,000 genes are located here and if there is an error in this blueprint, diseases can arise. Certain genetic defects can lead to very specific ailments and can also be inherited. Scientists are trying to read such errors in the genome better and interpret them correctly in order to enable healing with this knowledge. Jörg Epplen, head of human genetics at the Ruhr University in Bochum, doesn't see science as far. 7,000 diseases that are triggered in whole or in part by certain genes are known in research, but only around half are able to find them through a genetic test. For example, breast cancer or Huntington's disease.
However, all this knowledge does not really help research much, "because - even if we know the problem in our genes - we still can't heal it," says Epplen. Only a dozen genetic diseases are actually treatable with gene therapy today, such as very rare defects in the immune system. To make matters worse, a genetic test does not reveal all connections, but only a small section of the genes of a cell.
Healthy lifestyle even with the best genetic conditions It would be wrong to rely on one's “good genes”, because lifestyle always plays a role, often even more important than the inherited factor. With a genetic test you can only get information on how likely the risk of an outbreak of a certain disease is, but only statistically. The doctor says: "Because even with the best genetic conditions, an unhealthy lifestyle could lead to a heart attack, for example." A person's health future cannot therefore be automatically predicted using genetic diagnostics.
Life-saving knowledge through genetic tests Everyone has to decide for themselves whether they should know at all whether they are statistically at risk of getting a certain disease. Epplen says: "In fact, knowledge about it can sometimes make sense." For example, it is known that the mutant gene that Angelina Jolie carries can cause breast and ovarian cancer in women and prostate cancer in men. If those affected know about the likelihood of an illness, they can opt for close preventive care so that an outbreak of the disease can be recognized immediately and thus possibly treated in a life-saving manner. However, Epplen also warns: “One should be clear, however, that such tests do not only bring clarity. They can also be very stressful psychologically. ”
Controversial preimplementation diagnosis Another example is genetic Huntington's disease, which is not curable and about 50 percent is passed on to children. Such inheritance would be avoidable if preimplantation diagnosis (PID) was used. In PID, after artificial insemination in a test tube, a cell with genetic information about the possible fetus is removed and, if the gene in question is present, parents have the option of deciding against the baby. In Germany, PGD is only permitted to avoid serious hereditary diseases and stillbirths or miscarriages. A PID may only be carried out in specially certified centers. It is prohibited in Switzerland and Austria. In a press release, the German Ethics Council warned that those affected often received "incriminating information without the possibility of intervention".
Right to not know However, some parents also have their unborn babies tested for genetic defects in the womb, including Trisomy 21, the so-called Down syndrome. In the past, such tests were carried out using invasive measures such as amniotic fluid or mother cake tests. In the meantime, however, the blood of the pregnant woman from the tenth week of pregnancy can be predicted with certainty whether the possibility of trisomy 21 exists. Epplen adds: “When it comes to so-called genetic counseling, we always point out the right not to know what one's own genetic disposition is,” and many people made use of this right.
Expensive and time-consuming research still takes decades. The challenge for science in the future will be to determine the genetic connections between common diseases such as Alzheimer's or colorectal cancer, blood sugar, high blood pressure, heart attacks or Parkinson's disease. In order to meet this challenge, complex and expensive research is necessary. The expert also said: "The difficult thing is that we do not know which combination of gene changes make how sick - and which are completely harmless." And further: "It will take us decades to understand the genetic connections here very precisely."
A little optimism An obstacle to fully understanding and correctly interpreting genes is that not all genes are inherited. Rather, some places are so-called new mutations, which first appear in the examined person. In addition, the programs for predicting the significance of certain gene variations are currently contradictory and therefore completely inadequate. So there is a need for great progress in terms of interpretation. Therefore, new processes would have to be developed and significant progress can only be expected in a few areas in the next three to five years. However, the scientist Epplen still exudes a bit of optimism: "In ten years we will not yet know all the genetic combinations that are dangerous - but we will certainly determine all those genes that are solely responsible for a certain disease." (sb)
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