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Investigating the Relationship Between FMR1 Allele Length and Cognitive Ability in Children: A Subtle Effect of the Normal Allele Range on the Normal Ability Range?
Author(s) -
Loat C. S.,
Craig G.,
Plomin R.,
Craig I. W.
Publication year - 2006
Publication title -
annals of human genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.537
H-Index - 77
eISSN - 1469-1809
pISSN - 0003-4800
DOI - 10.1111/j.1469-1809.2006.00269.x
Subject(s) - fragile x syndrome , allele , fmr1 , genetics , trinucleotide repeat expansion , cognition , biology , audiology , fragile x , ataxia , intelligence quotient , allele frequency , psychology , medicine , gene , neuroscience
Summary The FMR1 gene contains a trinucleotide repeat tract which can expand from a normal size of around 30 repeats to over 200 repeats, causing mental retardation (Fragile X Syndrome). Evidence suggests that premutation males (55‐200 repeats) are susceptible to a late‐onset tremor/ataxia syndrome and females to premature ovarian failure, and that intermediate alleles (∼41‐55 repeats) and premutations may be in excess in samples with special educational needs. We explored the relationship between FMR1 allele length and cognitive ability in 621 low ability and control children assessed at 4 and 7 years, as well as 122 students with high IQ. The low and high ability and control samples showed no between‐group differences in incidence of longer alleles. In males there was a significant negative correlation between allele length and non‐verbal ability at 4 years (p = 0.048) , academic achievement in maths (p = 0.003) and English (p = 0.011) at 7 years, and IQ in the high ability group (p = 0.018) . There was a significant negative correlation between allele length and a standardised score for IQ and general cognitive ability at age 7 in the entire male sample (p = 0.002) . This suggests that, within the normal spectrum of allele length, increased repeat numbers may have a limiting influence on cognitive performance.