Cracking the human genome is a dense and seemingly impenetrable undertaking, what with our 46 chromosomes, more than 30,000 genes and 3 billion base pairs: It's hard to imagine that some tiny variation embedded in the middle of all that code could actually predict something like who will have to retake driver's ed three or four times just to pass the driving test.
Well, it can. In fact, according to a new study by researchers at UCI, a tiny variant in the genetic code can help predict whether its owner will be a lousy driver. Their study is published in a recent issue of the journal Cerebral Cortex.
Seven in 10 of us carry genetic instructions to flood certain regions of the brain with a neurochemical called brain-derived neurotrophic factor -- or BDNF -- when we're challenged to learn a new aerobics routine, land a plane or navigate a tricky patch of road. It seems to help us learn to do new things.
But 30% of humans have a small variant in their genetic code that results in the release of smaller doses of BDNF when they're trying to master a new skill that involves physical coordination. These people have brains that are smaller in some key regions. Researchers have observed that when people with this genetic variant suffer a stroke with loss of motor function, they recover more slowly and less completely than those without the variant.
Could it be, asked researchers in the lab of UCI neuroscientist Steven Cramer, that when it comes to learning new things, this 30% of humans is just not as fast on the uptake?
To see, Cramer's team ran a series of experiments culminating in the driving challenge: 22 subjects had the genetic code that ordered up lots of BDNF when it came time to learn a new trick; seven had the genetic variant that coded for the release of less BDNF. Earlier experiments had already shown that compared with the smaller group with the genetic variant, the brains of those in the large group responded to the challenge of a new physical task with stronger activity in many more regions.
In the driving challenge -- learning to steer down a simulated winding road without drifting off the center line -- the group with the genetic variant made 20% more errors than the larger group, were slower to learn and, when tested again four days later, forgot more of what they had learned than had their peers without the variant in the BDNF gene.
Cramer said his team was astonished that a single-nucleotide polymorphism -- sometimes called a SNP -- would seem to yield such distinct differences in actual everyday behavior. Whether it influences how we learn every new task or has a cumulative effect in shaping the brain, said Cramer, this tiny genetic variant is powerful.
"Next time someone cuts you off on the freeway, one could conjecture that this could be part of the problem," said Cramer in an interview. (He adds that this knowledge hasn't make him feel more kindly toward offending motorists though.)