Researchers make the assumption that if 1000 people share the same disease they should also share the genetic mutations that contribute to that disease. If researchers can pinpoint the genetic differences that all these people share — genetic mutations that healthy people don't have — they can understand how these mutations contribute to a disease. By understanding the cause, they can hopefully find a treatment.

In an ideal world, researchers would just sequence the genomes of all 1,000 people - effectively lay them side-by-side and compare the sequence of the As, Cs, Gs and Ts in each person's DNA. That would show them the mutations that people with the disease share and scientists would start their research there. Unfortunately, with current technology, sequencing the 3.1 billion bases in a single human genome is too expensive and time consuming to be practical for disease research. After all, it took the Human Genome Project 10 years to sequence a single human genome. SNPs offer a more practical way to find the genetic differences that cause disease.