Behavior Genetics

, Volume 24, Issue 2, pp 107–118

DNA markers associated with high versus low IQ: The IQ quantitative trait loci (QTL) project

  • Robert Plomin
  • Gerald E. McClearn
  • Deborah L. Smith
  • Sylvia Vignetti
  • Michael J. Chorney
  • Karen Chorney
  • Charles P. Venditti
  • Steven Kasarda
  • Lee A. Thompson
  • Douglas K. Detterman
  • Johanna Daniels
  • Michael Owen
  • Peter McGuffin
Article

Abstract

General cognitive ability (intelligence, often indexed by IQ scores) is one of the most highly heritable behavioral dimensions. In an attempt to identify some of the many genes (quantitative trait loci; QTL) responsible for the substantial heritability of this quantitative trait, the IQ QTL Project uses an allelic association strategy. Allelic frequencies are compared for the high and low extremes of the IQ dimension using DNA markers in or near genes that are likely to be relevant to neural functioning. Permanent cell lines have been established for low-IQ (mean IQ=82;N=18), middle-IQ (mean IQ=105;N=21), and high-IQ (mean IQ=130;N=24) groups and for a replication sample consisting of even more extreme low-IQ (mean IQ=59;N=17) and high-IQ (mean IQ=142;N=27) groups. Subjects are Caucasian children tested from 6 to 12 years of age. This first report of the IQ QTL Project presents allelic association results for 46 two-allele markers and for 26 comparisons for 14 multiple-allele markers. Two markers yielded significant (p<.01) allelic frequency differences between the high- and the low-IQ groups in the combined sample—a new HLA marker for a gene unique to the human species and a new brain-expressed triplet repeat marker (CTGB33). The prospects for harnessing the power of molecular genetic techniques to identify QTL for quantitative dimensions of human behavior are discussed.

Key words

Cognitive ability intelligence IQ quantitative trait loci (QTL) allelic association DNA markers 

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Copyright information

© Plenum Publishing Corporation 1994

Authors and Affiliations

  • Robert Plomin
    • 1
  • Gerald E. McClearn
    • 1
  • Deborah L. Smith
    • 1
  • Sylvia Vignetti
    • 1
  • Michael J. Chorney
    • 2
  • Karen Chorney
    • 2
  • Charles P. Venditti
    • 2
  • Steven Kasarda
    • 2
  • Lee A. Thompson
    • 3
  • Douglas K. Detterman
    • 3
  • Johanna Daniels
    • 4
    • 5
  • Michael Owen
    • 4
    • 5
  • Peter McGuffin
    • 4
  1. 1.Center for Developmental and Health GeneticsPennsylvania State UniversityUniversity Park
  2. 2.Department of Microbiology and ImmunologyPennsylvania State University, Milton S. Hershey Medical CenterHershey
  3. 3.Department of PsychologyCase Western Reserve UniversityCleveland
  4. 4.Departments of Psychiatry and GeneticsUniversity of Wales College of MedicineCardiffUK
  5. 5.Department of PsychiatryUniversity of Wales College of MedicineCardiffUK

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