The big data-mining companies play this game of lex loci server all the time: "Oh we are not really in country X, we're in California, that's where our computers are".
Rather, they are the tail ends of statistical distributions that reflect the shuffling of myriad, tiny genetic effects called quantitative-trait loci, whose true nature is not yet understood.
It is indeed a weakness of the current state of knowledge that individual quantitative-trait loci have not yet shown up.
Instead, Ms Asbury and Mr Plomin prescribe a revolution and an expensive one, at that.Their big idea is that, because of all those quantitative-trait loci, every child needs a unique curriculum.
The paper's authors are thus able to say that three-quarters of the loci they fingered contain a gene or genes, and a further 8% are close to one.
And just this week a paper in Psychiatric Genetics, on a single glutamate-related gene, GRM3, has shown it is connected both to schizophrenia and depression, and also to alcoholism.It will therefore be interesting to repeat the approach this study used to try to create comprehensive lists of loci for these other conditions.
The result is the most comprehensive investigation so far of the genetics of a psychiatric disorder.Locus standiAltogether, the paper's authors have discovered 108 places in the human genome, known as loci, where a change in a single DNA "letter" (a single nucleotide polymorphism, or SNP) correlates with the manifestation of schizophrenia.
In addition, it is precisely because Shenzhen is a hub of innovative IT production (and not high-end research) that it is now the loci of the most feverish hardware startup activity worldwide.
If the two loci are perfectly linked, then the set of gametes produced by the A1B1 / A2B2 double heterozygote has the composition {½ A1B1, ½ A2B2}; this means that if a gamete receives the A1 allele at the A locus, it necessarily receives the B1 allele at the B locus and vice versa.
It is easy to see that r = ½ means that the loci are unlinked, so all four gamete types are produced in equal proportion, while r = 0 means that they are perfectly linked.
There is an alternative body of theory, known as quantitative genetics, which deals with so-called 'polygenic' or 'continuous' traits, such as height, which are thought to be affected by genes at many different loci in the genome, rather than just one or two; see Falconer (1995) for a good introduction.
