Simple genetic diseases, such as cystic fibrosis and thalassaemia are just that — simple. A single gene underlies them. Finding it is like climbing a steep hill — hard work but straightforward. Complex disorders, such as asthma and type 2 diabetes, by contrast, have many components, which makes finding a cause more like scaling Everest — far harder, requiring more specialist equipment and the strong possibility of failure.
In work published in the October issue of