posted 03-20-2003 01:52 PM            

In February 2003 the discovery of the genes underlying taste sensitivity to phenylthiocarbamide (PTC) was published by D. Drayna and coworkers (see http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12595690&dopt=Abstract and http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12624758&dopt=Abstract
In 1969 during my first empirical study I tested several hundred subjects for their ability to taste PTC, and I tried to find the optimal threshold to separate the overlapping distributions of tasters from non-tasters. Since 1931 many authors believed that a simple two-allele model of a single locus could fit the genetics of PTC-tasting sensitivy. However, I remember vividly a case in the village, where my wife comes from and where I tested the whole population, that in one family either the genetic model was wrong or one child illegitimate. The most simple explanation for such irregularities has always been the hypothetical existence of a third allele with low frequency. Indeed, such an allele has now been discovered. However, because the distribution of PTC-tasting sensitivity is a quantitative one, in the meantime some authors had rejected the simple major gene model. Heritabilities were calculated, models of polygenic inheritance were advocated and occam’s razor was replaced by the usual nonsense of argumentation and counterargumention. Therefore, for me, the discovery by Drayna is not only a triumph of science, but also a model of hope.
Already in November 1990 I came on the basis of empirical data to the conclusion that a major gene of IQ must exist (see www.volkmar-weiss.de/majgenes.html and www.volkmar-weiss.de/ability.html . Where there is segregation within families following Mendelian rules there must be a underlying gene locus causing this segregation, and such a locus can be discovered (see www.volkmar-weiss.de/intellig.html . This is the iron logic of genetics. But in contrast to PTC the genetics of IQ is a political problem, too (see www.volkmar-weiss.de/lysenkoism.html .
When the effort and the methodological sophistication applied in the case of PTC-tasting sensitivity would be applied to the genetics of general cognitive ability, too, we will obtain a similar result within a comparable time span. Time is ripe now for such an approach. If you have only two men, a very intelligent one with an IQ of 135 and a mentally healthy one with an IQ of about 90, and you decode the sequences of these two men, there where the intelligent one is different from the less intelligent on both chromosomes, there could be the locus of IQ. To exclude decoding errors you need not one but about 5 men of each mental class.
Since about 30 years there are lot of well-known and well-confirmed correlations between IQ and short-memory scores on the one had and biochemical variables on the other. But the metabolic network around glutathione, methionine, homocysteine (see www.volkmar-weiss.de/homocysteine.html ) and other biochemical compounds is an intricate one and the number of possible genetic polymorphisms large. In 1995 after my publication in “Intelligence” (1994) all known genetic polymorphisms of glutathione peroxidases and glutathione transferase were investigated for any relationship with IQ and social status. But nothing could be found. But what about the newly discovered rs-7314-polymorphisms of 1-cysperoxiredoxin? (see http://www.ncbi.nlm.nih.gov/SNP/snp_ref.cgi?searchType=adhoc_search&type=rs&rs=7314 and http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10893423&dopt=Abstract ? On the genetic level the difference between an intelligent man and a less intelligent is not a matter of quantity, but of quality. The declaired aim of resarch should not be the genetical background of IQ, but the genetics of short term memory capacity and the discovery of targets for memory enhancing drugs. Which company is willing to open the race for hunting down this target? I would like to join in as adviser.