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When the infamous "Golden State Killer" – known for a series of rapes and murders in California in the 1970s and 1980s – was trapped last April, it sparked a sigh of collective relief. But the way the authorities discovered the killer – with the help of data from a genealogy website – has left people with troubling feelings about the power of genetic testing.
That's because his DNA caught the Golden State killer when the police compared the samples to those of his third cousin, who had uploaded genetic data into a genealogy database. Since then, the debate has revolved around the ethics of using genealogy websites to facilitate forensic investigations. [Genetics by the Numbers: 10 Tantalizing Tales]
And now, a new study shows how important these genealogy sites are. The researchers found that about 60% of people in a database of more than 1.2 million people could be associated with at least one other person in the database who was a third cousin or relationship even closer.
Indeed, a genetic database should cover only 2% of the target population to find at least one third cousin corresponding to almost any person, they wrote in the study published on October 11th. in the journal Science.
The group analyzed data from 1.28 million anonymous people on a genealogy site called My Heritage. (The lead author of the study, Yaniv Erlich, is the chief scientific supervisor of the site.) Comparing what's called progeny identification segments (ADIs) in the DNA, the server can locate even distant relatives, such as second or third cousins. The greater the number of IBDs shared between two people, the closer their relationship is.
The researchers targeted shared PCI segments that would correspond to the second, third and fourth cousins. They found that 60% of their searches matched – most of them were third-degree cousins or closer. The researchers then conducted a similar, but smaller, search on GEDmatch (the database used to catch the Golden State Killer) and found that 76% of their 30 random searches corresponded to a third cousin or closer.
In addition, they found that people of North European descent were the easiest to associate. About 75% of the people in the database came from northern Europe and 30% more likely to have a match than people of genetic origin from sub-Saharan Africa.
The team found that once these parents were located, the identity of the anonymous person could be easily determined by examining family lines and demographic information, such as the person's age or place of residence. They showed it by discovering the identity of an anonymous woman after finding her distant relatives.
Indeed, between April and August of this year, at least 13 cold cases in the United States (including that of the Golden State Killer) were resolved through such research, according to the study. What makes them so powerful, is that even though searches in court databases – which are strictly regulated – can only find close relatives at the first or second degree, research in the basics of genetic data can find more distant ones.
"While policymakers and the general public may be supportive of such improved forensic capabilities for crime resolution, they rely on databases and services that are open to all," the authors wrote. "Thus, the same technique could also be exploited for detrimental purposes, such as re-identifying research subjects from their genetic data."
The researchers suggest that policies be put in place to protect people's genetic data. They also recommend that genealogy sites begin to protect raw genetic data files with a secure digital signature in order to make access to these data more difficult.
Originally posted on Live Science.
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