Failure to replicate a QTL association between a DNA marker identified by EST00083 and IQ

Abstract

In a paper published in this journal, a possible QTL association was reported between general cognitive ability and a marker, identified by an expressed sequence tag, EST00083 (Skuder et al., 1995). In two small samples, the frequency of the common allele of this DNA marker, which was shown to be in the threonine transfer RNA gene in mitochondrial DNA, was significantly greater in a high-IQ group than in a low-IQ group. As part of the ongoing IQ QTL Project (Plomin et al., 1995), we have attempted to replicate this QTL association. First, we found that the QTL association remained significant when we compared 51 high- and 51 -average IQ subjects, drawn in part from the samples used in the previous report. However, when we examined the association in new samples of 40 extremely high-IQ subjects and 50 average-IQ subjects, the association did not replicate. This underlies the need for replication in case-control studies of allelic association.