“A Quantitative Trait Locus Associated With Cognitive Ability in Children”, 1998-05-01 (; backlinks):
Quantitative trait loci (QTLs) associated with general cognitive ability (g) were investigated for several groups of children selected for very high or for average cognitive functioning.
A DNA marker in the gene for insulin-like growth factor-2 receptor (IGF2R) on Chromosome 6 yielded a statistically-significantly greater frequency of a particular form of the gene (allele) in a high-g group (0.303; average IQ = 136, n = 51) than in a control group (0.156; average IQ = 103, n = 51).
This association was replicated in an extremely-high-g group (all estimated IQs > 160, n = 52) as compared with an independent control group (average IQ = 101, n = 50), with allelic frequencies of 0.340 and 0.169, respectively. Moreover, a high-mathematics-ability group (n = 62) and a high-verbal-ability group (n = 51) yielded results that were in the same direction but only marginally statistically-significant (p = 0.06 and 0.08, respectively).
[Warning: despite the replication, these candidate-gene hits were all false positives.]