It once was thought that, when we d finally figured out the human genome, we d have all of the answers to the genetic underpinnings of various diseases. A person who had his genome mapped would know all there was about his risk of disease. But now that the human genome has indeed been fully mapped, scientists are starting to realize that the process of understanding the genetic basis of disease is nowhere as simple.
Two articles in the journal Science found that it s not just common mutations that are responsible for common diseases in fact, common mutations explain only a small portion of a human s genetic risk of disease. Very rare genetic mutations are actually surprisingly abundant in the human genome and may form the basis of common diseases and disorders, such as cancer and schizophrenia. One of the studies, led by scientists from the University of Washington in Seattle, found that each person has about 313 genes (out of the total 25,000) that carry rare mutations altering the function of the protein the gene codes for. The other study, led by a team from GlaxoSmithKline, came to similar conclusions, finding that one in every 17 units of DNA has a rare variant.
The problem with figuring out how rare mutations affect disease is that such studies would require huge numbers of participants in order to single out the effects of these gene variants such studies would also, of course, be very expensive.
ACSH friend Dr. Derek Lowe, a pharmaceutical research chemist who writes the highly regarded blog In the Pipeline," has been following the human genome project since its inception. As Lowe explains, The total number of human genes turned out to be a lot less than many people thought. And, while sometimes single genes are destiny, as with some inherited metabolic diseases, most of the time, destiny shows up in a much more roundabout fashion. Your DNA is your DNA, but how (and when) it gets expressed, and what gets done to the proteins that get produced, is another story entirely.