Individual genes produce quite subtle effects, and the more we learn about DNA, the clearer it is that any particular gene's potential can be shut down or enhanced by complex biochemical pathways contingent upon things like sleep, nutrition and stress. A decade ago the field of behavior genetics was aflutter with the hope that molecular biology would home in on what makes each of us tick. We've learned that in psychiatric disorders, there are no single genes of really large effect. If there were, we'd have found them already. Genes for certain conditions, such as Huntington's or sickle cell disease, are known as simple Mendelian traits because they follow the straightforward model of inheritance noted by the Austrian monk Gregor Mendel last century.
Mendelian traits are like a trumpet call.
It's hard to distinguish them from the background noise. That behavior is a tricky business to predict was elegantly demonstrated by another study published in Science this month. The idea was to see whether they would act according to type. In some tests, genetically identical mice acted differently depending on the lab that tested them. But all three teams found that the serotonin-mutants didn't booze it up any more than the others.