June 20, 2008
DNA Used To Help Adoptees Find Surname
Consumer DNA tests are being used by male adoptees to predict the surnames of their biological fathers.
Adoptees are using the fact that men who share the same surname often have genetic similarities. By checking DNA databases for males sharing a genetic make-up similar to their own, adoptees can see if these men also share a surname. This process can provide the possible last name of the adoptee's biological father.The genetic similarities between men who share surnames occur in the Y chromosome, a package of genetic material passed on, more or less unchanged, from father to son - just like a last name.
The Y chromosome, which remains mostly unchanged when passed from father to son, shows the genetic similarities between men who share surnames.
According to the chief executive of US genetic testing firm Family Tree DNA, at least 30 men have found their "biological surname" through the company's Y search database. The Y search online database contains genetic information and surnames from 125,000 men.
"We now have a growing number of people who are adopted, who have tested with us and have matched several individuals with a particular surname, and maybe they haven't matched anyone else with a different surname," explained Bennett Greenspan.
"From that, they can get the idea that they have at least found the surname they need to start looking for in the town in which they were born."
Up to 67 genetic markers on the Y chromosome can be found using the test. For some adoptees, finding the surname of their biological father would be very difficult under another circumstance.
"That's the real miracle of the DNA test. The Y chromosome can act in a sense like a silver bullet." Greenspan said.
Professor of genetics at the University of Leicester, Mark Jobling said: "If you have a surname which is reasonably rare, but not so rare that the chances of another person being typed and going into that database are infinitesimal, then you could be in luck. There's a big gamble in doing it, but people sometimes say that if you're in a dark room then even a little light can be useful."
Adoptee Chandler Barber, a copywriter from Dallas, said he had learned about the possibility of finding his surname from a magazine article explaining consumer DNA testing.
The Y search database discovered 6 people who were close genetic matches of the surname Ritchie, including one US-based variation of Ruetschi who was an extremely close match.
"It was pretty concrete evidence," said Mr. Barber.
"It's a quick and effortless way to at least find some nugget about your history. I am sure there are people who have been searching for their birth parents on foot, with pen and paper, for years - and have got nowhere."
Edward Cerullo, a programmer from Norway, knew his biological father's surname "“ Page- before testing his DNA.
Mr. Cerullo explained: "When the results came back, of the 22 names they sent back who matched my DNA 11 were Page or Paige. That's statistically pretty hard to argue against."
The Y search database allowed Cerullo to see how his personal line of descent fit into the wider family tree for this last name.
The link between surname and genetic similarity on the Y chromosome gets stronger, with the uniqueness of the last name. "Even in reasonably common surnames you see 'descent clusters,'" said Mark Jobling.
"In a name like Jefferson, for example, which is quite a common name, you find lots of these little descent clusters. There is identity within those clusters but there are many of them. In a name like Attenborough, there is just one great descent cluster...There's a spectacular common ancestry for that name."
Jobling cautioned that these patterns could differ from nation to nation. Also, the process can cause some false matches when rare markers run across multiple surnames.
Some false matches can also appear from technical issues with DNA databases. For example, confusion can arise when testing companies use different names for genetic markers. A customer whose DNA was tested by various companies may run into problems if their genetic information is submitted to the same database.
Mark Jobling said tests offering better solutions on the entire genome should be able to solve family puzzles in the future. In the early 20th Century, children born out of wedlock were sometimes raised by the grandparents as their own. One man, Jobling recalled, suspected this had been the situation with his family. His mother, the individual believed, was actually his "older sibling." Unfortunately, the parents and sister were deceased.
Professor Jobling explained: "If there is another relative, such as an acknowledged grandchild of this grandparental/parental couple, you can set up a hypothesis whereby you say: 'if they were his parents, how much of his DNA should he share with this cousin. If they were his grandparents, he should share a certain lesser proportion of his DNA with his cousin. You can distinguish the two scenarios."
According to Jobling, the falling costs of grouping entire genomes offer the promise of finding genetic variants that are particular to one surname.
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