A startling recent discovery has overturned much of what we know about disease. As usual, Nicholas Wade in the New York Times sums it up well:
- Until [recently,] researchers have looked only at common mutations as possible contributors to the risk of common diseases. [However] common variants have turned out to explain only a fraction of the genetic risk of common disease.
- It now appears that large numbers of very rare genetic mutations may underlie common human diseases like schizophrenia and cancer.
What's it all mean? Certainly it will be difficult to map every single DNA unit to a disease, as there are 3 billion DNA units in each person, and "only" 7 billion people in the world. Everyone will have a different response to drugs, with no simple genetic test.
Nicholas Wade goes on:
- A rare variant occurs in one out of every 17 DNA units, of which the human genome has some three billion. 313 genes out of the 25,000 in the human genome carry rare mutations.
- Detecting the roots of common disease will [now] prove much more difficult. Mutations with small effect must be studied in large numbers of patients to be detectable ... raising doubts as to how soon genome sequencing will become a routine medical test.
- Rare mutations [may be] specific to particular populations, with Africans and Europeans having sets that do not overlap much. This means that medical knowledge about rare mutations may have to be developed independently for each population.