Update 7/20/2012: The Rare SNP feature has been moved from Gedmatch to another website. I think we can expect that there will soon be information on Gedmatch.com about how to access the new website.
Using your autosomal DNA results, which are easy to load up to Gedmatch.com, you can search for rare SNPs you have in common with one other person (whose kit number you know). You could compare yourself to a close or distant relative. I tried it and found it pretty easy to do and the results are fascinating to read. What is an SNP? you may ask. An SNP is just short for SNiP, a snip, or section of DNA that can be compared to the same sections of DNA for another individual. Working with SNPs, we can find commonalities which point to how related or unrelated we are to another person, or we can look at decoding the messages in the SNPs.
The utility works very quickly. Enter the kit numbers, click to compare, and boom! It is there before you.
Then you can see what scientific abstracts have to say regarding these SNPs and their correlation to health issues. I wish I could understand those abstracts better, but at least I can see what the headings are and know that the SNPs are (possibly) relevant to certain health matters, whether in a positive or negative way. For example: you may see that a certain SNP has been researched in regard to certain addiction issues or cancers. Your particular mutations are relevant, and the way in which they are relevant is explained. You can see the information and the source of the research.Very intriguing, and for those scientifically-inclined, it should be quite interesting to ponder.
Again, we have a new and useful feature from Gedmatch.com.
This is the websites's description of the feature, and they say it better than I can:
"This utility finds rare SNPs that are shared by more than one person.
It may be useful for identifying SNPs from deep common ancestry,
or SNPs related to shared characteristics."
image from Coriell Personalized Medicine Collaborative