IQ and gene link confirmed

Repeated twin studies stretching back for around a century have shown that IQ is highly genetic. But it seems most likely that high IQ reflects good functioning in several areas or aspects of the brain. High IQ could be seen as all the brain working well together in a perfect symphony. So it has long been thought that many genes would be involved. The study mentioned (excerpts) below appears to have isolated one of the more significant genes. You are most UNLIKELY to learn of the findings below in the Media

If you're particularly good with puzzles or chess, the reason may be in your genes. A team of scientists led by School of Medicine psychiatric geneticists has gathered the most extensive evidence to date that a gene that activates signaling pathways in the brain influences one kind of intelligence. The researchers confirmed a link between the gene CHRM2 and performance IQ, which involves a person's ability to organize things logically.

"This is not a gene for intelligence," said Danielle M. Dick, Ph.D., assistant professor of psychiatry and lead author on the study. "It's a gene that's involved in some kinds of brain processing, and specific alterations in the gene appear to influence IQ. But this single gene isn't going to be the difference between whether a person is a genius or has below-average intelligence." .... [But it will raise your chances of being generally bright]

Dick's team comprehensively studied the DNA along the gene and found that several variations within the CHRM2 gene could be correlated with slight differences in performance IQ scores, which measure a person's visual-motor coordination, logical and sequential reasoning, spatial perception and abstract problem-solving skills. When people had more than one positive variation in the gene, the improvements in performance IQ were cumulative.

The study's findings are available online in Behavior Genetics at bga.org and will appear in an upcoming print issue of that journal. IQ tests also measure verbal skills and typically include many subtests. For this study, subjects took five verbal subtests and four performance subtests, but the genetic variations influenced only performance IQ scores.

By comparing individual differences embedded in DNA, the team zeroed in on CHRM2, the neuronal receptor gene on chromosome 7. The CHRM2 gene activates a multitude of signaling pathways in the brain involved in learning, memory and other higher brain functions. The research team doesn't yet understand how the gene exerts its effects on intelligence....

Dick's team is not the first to notice a link between intelligence and the CHRM2 gene. In 2003, a group in Minnesota looked at a single marker in the gene and noted that the variation was related to an increase in IQ. A more recent Dutch study looked at three regions of DNA along the gene and also noticed influences on intelligence.

More here

Journal abstract from Behavior Genetics, Volume 37, Number 2, March, 2007:

Association of CHRM2 with IQ: Converging Evidence for a Gene Influencing Intelligence

By Danielle M. Dick et al.

The cholinergic neurotransmitter system is thought to be involved in many aspects of memory, attention, and higher cognition. In the Collaborative Study on the Genetics of Alcoholism (COGA) sample, we have previously reported linkage and association to the cholinergic muscarinic 2 receptor gene (CHRM2) on chromosome 7 with evoked EEG oscillations (Jones et al. 2004), providing evidence that this gene may be involved in human brain dynamics and cognition. In addition, a small number of genetic markers were genotyped in CHRM2 in the Minnesota Twin and Family Study (Comings et al. 2003) and a Dutch family study (Gosso et al. 2006, in press) and both research groups found evidence that this gene may be involved in intelligence. In the COGA sample, we have extensively genotyped SNPs within and flanking the CHRM2 gene. We find evidence of association with multiple SNPs across CHRM2 and Performance IQ, as measured by the Wechsler Adult Intelligence Scale-Revised (WAIS-R). These results remain significant after taking into account alcohol dependence and depression diagnoses in the sample.

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