Look for the cluster

Genetic differences between individuals come in big chunks just like
self-assembly furniture. While studying the bowel disorder Crohn’s disease, Mark
Daly, Eric Lander and their team at the Whitehead Genome Center in Boston found
that genetic defects which make people susceptible to the disease lie in
clusters or “haplotypes” at specific regions on chromosomes. They urge
biologists to make a comprehensive map of these DNA chunks to help doctors spot
patients at high risk of any disease with a genetic link (Nature
Genetics, vol 29, p 223 and p 229).