By Janet Fang
Posting in Education
Using brain scans and DNA samples from over 20,000 people, an international team discovered 2 interesting genetic variants: one affects IQ and brain size, another affects memory.
Looking at fMRI brain scans and DNA samples from 21,151 people, researchers reveal that a single gene has an impact on intelligence.
The effect is small – a bit more than 1 point – but it’s the biggest effect of a single gene on IQ known so far. New Scientist reports.
It’s not surprising that genetics would account for a large amount of variation in our intelligence, but experts typically find that hundreds of genes contribute, with no one taking all the credit.
An international collaboration of 207 researchers, the Enhancing Neuro Imaging Genetics through Meta-Analysis (ENIGMA) Consortium, was able to tease out a single gene: HMGA2, previously linked with height.
Its effect is small but measurable: it alters IQ by 1.29 points. When people inherit the variant from both parents, they enjoy double the effect: a rise in IQ of about 2.6.
At the site of the relevant mutation, the IQ difference depends on a change of a single DNA letter: from C to T, with C being the “good one,” says study researcher Paul Thompson of the University of California, Los Angeles.
C, or cytosine, raises IQ and even increases the overall volume of the brain… by 0.58% of average brain size. "It's a loss or gain of about 2 teaspoons," Thompson explains.
The research also revealed that a variant of a gene called TESC affects the size of the hippocampus, a memory part of our brain. The gene alters hippocampal size by 1.2% above or below the average.
In adulthood, the hippocampus shrinks by about 0.5% per year, so having that particular gene variant can equate to more than 2 years of aging. Having 2 copies of it is equivalent to 5 years of aging.
Other contributors, such as a good education, exercise, and other environmental factors, could outweigh the effect of single gene variants. But these 2 variants could help improve diagnosis and eventually treatment of brain disorders.
The findings were published in Nature Genetics this week.
Image of fMRI via Flickr
Apr 16, 2012
The end of the article mentioned TESC as effecting the hippocampus size and that in adulthood the hippocampus shrinks .5% annually. I find this to be interesting in that this can explain how memory changes as we age; some seniors seem to be bad at forming new memories but are good at remembering old memories from childhood and early adulthood. Intelligence is a tricky aspect to measure. IQ is supposed to be a measure that shows intelligence compared to others of the same age with 100 being the median value. The problem with IQs is that it is hard to measure actual intelligence but easy to measure learned intelligence.
Most who study the field of human intelligence would agree that our current efforts to both define and measure human intelligence is very limited - and basically inadequate. To assume that you are measuring 1-2 point differences in an IQ scale says more about the level of knowledge the researcher has regarding the state-of-the-art of IQ measurement and its limitations, than it does about any potential genetic differences. The final admission of the article is probably the most accurate statement in its entirety - "Other contributors, such as a good education, exercise, and other environmental factors, could outweigh the effect of single gene variants." So, can we conclude that in this experiment we can't be sure whether genes or experience might have had the most affect and were they able to separate exactly which - meaning the value of this study is exactly what? Well, that would be "nothing" for sure - exactly.