It's possible, but it would be quite a stroke of luck. The SNP is a mutation and could be part of the problem, but scientists think that most SNPs have no effect at all. For a researcher, a SNP's primary function is to serve as a marker, or a sort of sign post along the genome that says to the researcher: "Out of the 3.1 billion base pairs in the human genome that could have mutations that cause this disease, you might start looking here, around this SNP which everyone with the disease shares." SNPs are not the only types of mutations either. Deletions and duplications of DNA can also cause disease, but by analyzing SNPs, scientist have a way of finding any kind of mutation linked to disease.

By definition, any single base pair that is different from the reference sequence drafted by the Human Genome Project is a SNP. But if, say, only five people in the world share the same SNP, it's not going to be much good to researchers that are trying to find genes associated with diseases. If you have a list of 10,000 SNPs and you want to see if a group of 100 people with colon cancer share any of them, you probably won't get many matches if the SNPs you have only appeared in a handful of people in the population. You want the popular SNPs, the ones that show up a lot. Remember, the SNP&39;s purpose is to point you to a block of DNA that people in the disease group share, it may not have anything to do with the disease.

If a SNP mutation has happened recently, not much time has elapsed to allow it to be transmitted and inherited by a large number of people. This kind of SNP is a rare SNP. On the other hand, if we are looking at a SNP mutation that happened 25,000 years ago, there's a much greater chance for that SNP to have been inherited by a lot more people. Scientists say that these types of SNPs are "common".