NEWSFLASH: gene expression is complicated
Carlborg and Haley, "Epistasis: Too often Neglected in Complex Trait Studies?" Nature Reviews Genetics 5 (2004), 618-625. Abstract:
Interactions among loci or between genes and environmental factors make a substantial contribution to variation in complex traits such as disease susceptibility. Nonetheless, many studies that attempt to identify the genetic basis of complex traits ignore the possibility that loci interact. We argue that epistasis should be accounted for in complex trait studies; we critically assess current study designs for detecting epistasis and discuss how these might be adapted for use in additional populations, including humans.Epistasis is a fancy way of saying that that multiple genes affect individual traits. I would argue that it is in part an intuitive grasp of this fact that makes people uncomfortable with the currently rather crude techniques of genetic engineering. There's more going on in the genome than 1 gene = 1 trait, and throwing foreign DNA at it and hoping something sticks (the fancy word for that is "microprojectile bombardment") seems like a good way to fuck up something more complicated than you understand. I'm just saying.