HLA-A and CTGB33 polymorphisms and variation in IQ scores

This study attempted to replicate findings of Plomin et al. (Plomin and Neiderhiser, 1991). DNA markers associated with high vs low IQ: The IQ quantitative trait loci (QTL) project, Behav. Genet., 24, 107–118) in which significant differences in allelic frequency at a locus in the HLA class I region and the triplet repeat, CTGB33 were found between low and high IQ subjects. The two IQ groups for our study were taken from a sample of elderly people whose IQ was assessed using a measure of intelligence that is highly resistant to the effects of ageing and dementia. The high IQ group had an average IQ of 125 while the lower groupʹs average IQ was 95. No difference was found in the allelic frequencies for any of the CTGB33 alleles or the HLA-A alleles. As there were a number of differences between this study and that of Plominʹs group, this can only be viewed as a limited attempt at replication.