"To What Extend Are Genetic Variation and Personal health Linked?" is one of the top 25 questions from the 125th anniversary issue of Science magazine [Science, July 1, 2005]. The complete reference is ...
Jennifer Couzin is a San Francisco-based news writer for Science magazine. She writes mostly on health-related issues and received the 2003 Evert Clark/Seth Payne Award for excellent science writing by a young journalist [Science Writers Honor One of Their Own].
The question may seem strange at first but don't be misled. Nobody is questioning whether there's a link between human diseases and genes/alleles. The question is exactly what it seems—how much linkage is there? It's the nature vs nurture question and that's surely an interesting question.
As Couzin writes,
These developments have led to hopes--and some hype--that we are on the verge of an era of personalized medicine, one in which genetic tests will determine disease risks and guide prevention strategies and therapies. But digging up the DNA responsible--if in fact DNA is responsible--and converting that knowledge into gene tests that doctors can use remains a formidable challenge.I like the sound of this. It shows that she's skeptical of the exaggerations in the scientific literature and that's good. It's what a science writer should be doing.
Many conditions, including various cancers, heart attacks, lupus, and depression, likely arise when a particular mix of genes collides with something in the environment, such as nicotine or a fatty diet. These multigene interactions are subtler and knottier than the single gene drivers of diseases such as hemophilia and cystic fibrosis; spotting them calls for statistical inspiration and rigorous experiments repeated again and again to guard against introducing unproven gene tests into the clinic. And determining treatment strategies will be no less complex: Last summer, for example, a team of scientists linked 124 different genes to resistance to four leukemia drugs.
But identifying gene networks like these is only the beginning. One of the toughest tasks is replicating these studies--an especially difficult proposition in diseases that are not overwhelmingly heritable, such as asthma, or ones that affect fairly small patient cohorts, such as certain childhood cancers. Many clinical trials do not routinely collect DNA from volunteers, making it sometimes difficult for scientists to correlate disease or drug response with genes. Gene microarrays, which measure expression of dozens of genes at once, can be fickle and supply inconsistent results. Gene studies can also be prohibitively costly.
The problem is, this isn't one of the top 25 mysteries in science by any stretch of the imagination. We don't know the answer but that's because we don't yet have enough data. I don't think there's any profound scientific problem here. Some links between genes and disease are very clear [e.g., Glycogen Storage Diseases] and some will be more difficult to work out. Some diseases may not have a genetic component at all.
It's good to be skeptical about the rhetoric that comes out of the medical literature but the top questions in science should not be about medicine of technology and they should not be about things where we're just waiting for more data.