What can genetic testing tell us?
You can now order personal genetic tests online for under USD 200. But can they tell you if your child will be a whiz at school or a soccer star?
The technology for mapping DNA has developed enormously in the past decade. Today’s methods are very effective and getting cheaper. Businesses have swooped in to take advantage of the technology.
On the website of the American Map My Gene, customers are offered an opportunity to find out not only what diseases they are particularly vulnerable to, but also what sort of talents they and their children have entered the world with. For instance if you find out that your children have what it takes for soccer or some other sport, you can raise them with this in mind in order to exploit their potential.
Earlier this week the Norwegian Biotechnology Advisory Board staged a panel debate in Oslo about the problems of genetic testing of children for school and sports.
Bjørn Myskja, the vice-head of the Advisory Board, said that claims like those on the website Map My Gene are currently nonsense, but they could pan out in the future.
Abilities are hard to map
What can be ascertained by genetic tests today?
The relationship between genes and actual characteristics are highly complex. Genes interact with each other and with the environment.
Lars Wichstrøm, a psychology professor at the Norwegian University of Science and Technology (NTNU), illustrates how complicated it is to find out what particular genes do.
Your height is strongly determined by your genes, as it is largely inheritable.
Scientists have mapped over 670 different genes linked to height in a study of over 230,000 persons. But these genes were only found to predict 16 percent of heights in the test population.
The trait we call intelligence consists of multiple components. Intelligence and personality are very likely to involve many more genes than height.
“A truly comprehensive study would be required to identify enough genes to make an accurate estimate of intelligence. It would involve the genetic testing and IQ testing of many millions of people. This would take a long time. Another issue is who would finance and implement such a project,” said Wichstrøm.
Tape measures and stopwatches
Are there any genetic tests at all that say how good a person can be at something?
“Genes for really simple features, such as which type of muscle fibre you have most of – short and explosive rather than long – or traits like height are pretty well mapped,” said Wichstrøm.
In fact, a test of muscle fibre can be bought at pharmacies.
“But a genetic test cannot give more information about potential sprinting abilities than the traditional 60-metre races run at school.”
As for height, Wichstrøm says a yardstick or a tape measure is a far better tool for predicting future adult height of children than genetic tests can offer.
“By looking at the height of the parents you can be very accurate in calculations of a child’s height. It’s much better than a genetic test,” asserted Wichstrøm.
Talent requires training
“Gene mapping is useful now in medicine because we know of individual genes that link to a susceptibility to certain diseases,” said Lars Engebretsen in the panel debate. He is a professor of medicine at the University of Oslo and the Norwegian School of Sport Sciences.
But he stresses that there are no such DNA tests showing whether a child will be a future star in sports.
“There is no specific gene for running fast. Even though there are certain genes linked to various traits, that doesn’t mean you can predict abilities and talents. Other factors are much more important,” said Engebretsen.
If we find a gene that indicates how skilled a little girl will become at long-distance races, training will have an enormous impact on how good she becomes in such endeavours.
“It’s essential to keep the focus on genes from overshadowing the fact that excelling in sports requires years of intense training and a beneficial environment,” said Engebretsen.
Some swayed more
In addition to the complicated interplay of genes, there is still the old issue of genetic traits and their interaction with a social and physical environment – nature and nurture. Some individuals have genes that make them more easily affected than others.
Wichstrøm drew attention to a study of depression which showed that the some people became less depressed than others when exposed to the same stressful occurrences. This linked to a gene type which determines the transport of the neurotransmitter serotonin. Researchers concluded that how much a person is affected by circumstances depends on which variation they have the gene.
When these results were eventually applied to a larger study, no such link was found.
Then another study was done with an even larger cohort of 40,000 and the researchers found the effect once again.
“But if you have to test 40,000 persons to find an effect, then the effect is minimal,” claimed Wichstrøm.
He explains that the problem in determining the correlation between genes and particular characteristics is that there are far too many variables in the mix. The interplay among many genes and variations of genes and the relationship between genetic makeup and environment yield so many possible results.
“Much of what we have found about genes can be false positive results, which are merely incidental. Scientists still have a long way to go in understanding the roles of most of our genes,” explained Wichstrøm.
Read the Norwegian version of this article at forskning.no
Translated by: Glenn Ostling