Barbaux, S., R. Plomin and A.S. Whitehead (2000)Polymorphisms of genes controlling homocysteine/folate metabolism and cognitive function. Neuroreport 11(5):1133-6.
"Elevated concentrations of the amino acid homocysteine and/or folate deficiency have been reported to affect neural development/function in both human patients and animal models. We have investigated the distribution of functional polymorphisms in genes involved in homocysteine/folate metabolism in children with high IQ and in children with average IQ. No differences in the frequencies of genetic variants in the methionine synthase or methylenetetrahydrofolate reductase genes were found. However, the cystathionine beta-synthase (CBS) 844ins68 allele was significantly underrepresented in children with high IQ. The mechanism by which a functional genetic variant in the CBS gene may influence cognitive function remains to be determined."

Et: Plomin, R. (1999) Genetics and general cognitive ability. Nature, 402(6761 Suppl):C25-9
"General cognitive ability (g), often referred to as 'general intelligence', predicts social outcomes such as educational and occupational levels far better than any other behavioural trait. g is one of the most heritable behavioural traits, and genes that contribute to the heritability of g will certainly be identified. What are the scientific and social implications of finding genes associated with g?"

Il y a toujours les problèmes d'objectivité dans la détermination de l'"intelligence", du "QI", du "g", qui me rendent très suspicieux quant aux résultats de ce genre d'études.

Que certains gènes puissent influencer les capacités cognitives, donc l'"intelligence", c'est un fait facilement observable dans les cas pathologiques ou la déficience est évidente:

Gecz, J. and J. Mulley (2000) Genes for cognitive function: developments on the X. Genome Res 10(2):157-63
"Developments in human genome research enabled the first steps toward a molecular understanding of cognitive function. That there are numerous genes on the X chromosome affecting intelligence at the lower end of the cognitive range is no longer in doubt. Naturally occurring mutations have so far led to the identification of seven genes accounting for a small proportion of familial nonspecific X-linked mental retardation. These new data indicate that normal expression of many more X-linked and autosomal genes contribute to cognitive function. The emerging knowledge implicating genes in intracellular signaling pathways provides the insight to identify as candidates other X-linked and autosomal genes regulating the normal development of cognitive function. Recent advances in unravelling the underlying molecular complexity have been spectacular but represent only the beginning, and new technologies will need to be introduced to complete the picture."

Les problèmes naissent quand on essaye de faire des catégories d'"intelligence" à partir de cas non pathologiques.

Jean-François

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