You didn't speak about the amount and reliability of prediction of IQ in your kind reply. I have referred to that publication. The publication by Deary and Johnson you link to was published in 2009. I was quoting a more recent publication by Wendy Johnson, a frequent co-author with Deary at Edinburgh, in one of my other replies in this thread. Here are a couple of publications by Deary, Johnson, and various co-authors with more recent publication dates than what you have kindly linked:

The review article "The neuroscience of human intelligence differences" by Deary and Johnson and Penke (2010)

http://www.larspenke.eu/pdfs/Deary_Penke_Johnson_2010_-_Neur...

"At this point, it seems unlikely that single genetic loci have major effects on normal-range intelligence. For example, a modestly sized genome-wide study of the general intelligence factor derived from ten separate test scores in the cAnTAB cognitive test battery did not find any important genome-wide single nucleotide polymorphisms or copy number variants, and did not replicate genetic variants that had previously been associated with cognitive ability[note 48]."

Johnson, Penke, and Spinath (2011) "Understanding Heritability: What it is and What it is Not"

http://www.larspenke.eu/pdfs/Johnson_Penke_Spinath_2011_-_He...

"Presuming this is correct and, as Visscher and Keller appear to have implied, applicable to most behavioural traits, this indicates that literally thousands of genes are likely involved in each trait, with no single polymorphism having substantial effect, which is the quasi-infinite model to which Munafo and Flint refer. Whatever would we as psychologists do with such information?"

There are more publications on the issue where these came from. I am familiar with the current literature on the subject, both from an online discussion group hosted by the Behavior Genetics Association and from a weekly "journal club" during the school year (at which I met Wendy Johson, the co-author of the publication you linked to, and of other more recent publications I am linking to in this thread). The hope of many behavior genetics researchers was finding a simple genetic model of normal allele variation in just a few genes having a large and consistent influence on IQ in the normal range. That hope has been dashed by the data as further studies have been conducted, and as researchers attempt to replicate the studies of earlier authors in new data sets.