Individual Genes Are Just Not Very Informative. Call It Geno 's Paradox

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Individual genes are just not very informative. Call it Geno’s Paradox. We know from classic medical and behavioral genetics that many physical and psychological traits are substantially heritable. But when scientists use the latest methods to fish for the responsible genes, the catch is paltry.

Take height. Though health and nutrition can affect stature, height is highly heritable: no one thinks that Kareem Abdul-Jabbar just ate more Wheaties growing up than Danny DeVito. Height should therefore be a target-rich area in the search for genes, and in 2007 a genomewide scan of nearly 16,000 people turned up a dozen of them. But these genes collectively accounted for just 2 percent of the variation in height, and a person who had most of the genes was barely an inch taller, on average, than a person who had few of them. If that’s the best we can do for height, which can be assessed with a tape measure, what can we expect for more elusive traits like intelligence or personality?

Geno’s Paradox entails that apart from carrier screening, personal genomics will be more recreational than diagnostic for some time to come. Some reasons are technological. The affordable genotyping services don’t actually sequence your entire genome but follow the time-honored scientific practice of looking for one’s keys under the lamppost because that’s where the light is best. They scan for half a million or so spots on the genome where a single nucleotide (half a rung on the DNA ladder) is likely…

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