Editor’s note: Pending an FDA decision, 23andMe no longer offers new customers access to health reports referred to in this post. Customers who purchased prior to November 22, 2013 will still be able to see their health reports, but those who purchased after that time will not. Those customers will have access to ancestry information as well as access to their uninterpreted raw data.As the series Finding Your Roots with Henry Louis Gates, Jr. begins its 10-week run on PBS, The Spittoon will feature posts from 23andMe’s Ancestry Ambassadors featuring their own stories about using DNA to dig into ancestry.By Ann Turner, M.D.Many members of my extended family have inherited a mutation responsible for hearing impairment. The loss is detectable in childhood and progresses gradually over the years. I began wearing hearing aids forty years ago, when I was thirty. We have participated in several genetic studies over the years, but the cause has not been found yet. I decided to see how far I could get by testing cousins with and without the hearing impairment. With testing could I at least identify a chromosomal region shared by just the relatives with the condition? Family Inheritance: Advanced tool at 23andMe is an easy way to visualize the chromosomal regions shared by different relatives. The figure shows four of the people I tested. They share the hearing loss, come from different lines of descent, and are the most distantly related possible. (Closer cousins share so many segments that the target wouldn’t stand out.) The answer to my initial question is a resounding yes! Other extended families may be able to follow this model of collecting cousins, which I have also described in a column for the Journal of Genetic Genealogy. James Lupski has proposed the term “clan genomics” for this type of endeavor.Now what? The sense of hearing is complex, with numerous genes affecting structures and functions. To date, 122 different loci (that is, general locations) have been associated with hearing loss. The actual gene has been identified for only half of those. None of the locations overlap the section implicated in our family, so we are exploring virgin territory. We’ve reduced the possibilities from 3 billion bases and 20-some thousand genes to a mere 15,000,000 bases and 278 genes (many with unknown functions), but there’s still a ways to go. It’s highly unlikely that any of the SNPs in our genotype data from 23andMe are actually responsible, since the chip design focuses on relatively common variants. Thus I am participating in the exome pilot project at 23andMe, which will completely sequence the coding regions of all genes and (if we’re lucky) may identify a novel mutation. There may be no suspicious variants, or there may be a superabundance of potential candidates, but that’s part of the adventure.In the meantime, I am always on the lookout for even more distant cousins who might harbor the same mutation. Circumstantial evidence makes John Riley the more likely ancestor, but he is a brick wall in my genealogy. If the mutation originated with him, we might be the only people in the world to shed light on yet another gene important for the sense of hearing. If he inherited it from an ancestor, there might be other lines of descent out there who share some DNA with us in that part of chromosome 15. Either outcome would be intriguing.To be continued…23andMe’s services are not a substitute for professional medical or diagnostic advice. Always consult your physician for medical or diagnostic advice.Ann Turner received her undergraduate degree in biology in 1964 and her M.D. from Stanford University in 1970. Her interest in genealogy began in midlife, when she read a family memoir about her father’s ancestors coming to America in 1635 on the ship Abigail. She began thumbing through the passenger manifest, where she recognized another familiar name—one of her mother’s ancestors. One family had headed for Connecticut and another for Vermont. Their descendants—her mother and father—met and married 300 years later in Iowa.She founded the GENEALOGY-DNA mailing list at RootsWeb in the year 2000, the same week she received results from the first commercially available mtDNA test at Oxford Ancestors. She is the co-author (with Megan Smolenyak) of Trace Your Roots with DNA: Using Genetic Tests to Explore Your Family Tree and writes a regular column called ‘Satiable Curiosity for the Journal of Genetic Genealogy. She has consulted with Sorenson Molecular Genealogy Foundation and 23andMe.
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