My surname — Holden — has gone through many incarnations since it originated in England nearly 700 years ago.  Letters were added, then dropped.  Some branches of my family added an extra “u” in the middle, while others changed the pronunciation entirely.  Then, when my ancestors arrived in America over 200 years ago, the name went through a whole new set of changes.  It seems my surname has been in a constant state of change since its inception.

But the story of my surname is not unique.  Millions of Americans have similar stories about ancestors who, upon arriving in the New World, actively changed their names to sound more “American.” German immigrants named Blum became Bloom, Küsters became Custers, and Kÿfers became Coopers. Immigrants from Italy, Sweden, France, and countless other countries underwent similar transformations.  After just a few generations, the original spelling or pronunciation was lost.

Just as our surnames have changed over the centuries, little by little, so too has our DNA.  In fact, some regions of the human genome acquire mutations in such a way that researchers can trace the changes back through time – much like tracing a surname back for generations in a family tree.  And one region in particular, the Y-chromosome, happens to be passed down from father to son, the same way surnames are inherited in Western culture. That provides a wealth of opportunities for scientists from a variety of disciplines to use the Y-chromosome to unlock history’s secrets, unravel family trees, and even solve crimes.

The Genetic Legacy of the Vikings

The histories of Scandinavia and the British Isles have been entwined since Vikings from Norway and Denmark landed on the eastern coast of England in the year 792.  Successful raiding parties eventually led to settlements along the eastern half of England.  Today there are remnants of Viking settlements in this region in the form of place names, unique vocabulary, and even surnames.  Last year, British geneticists took surname information from an area formerly settled by Vikings to see if men living there today who had Scandinavian surnames also had evidence of Scandinavian (aka Viking) genetic ancestry.  They analyzed the Y-chromosomes of several hundred men, and, not surprisingly, found that those with Scandinavian surnames did indeed have Scandinavian DNA, at least on the Y-chromosome.  Similar studies of Irish men have also found a modest connection between surnames and Y-chromosome types.

Surname DNA Projects

As we reported several weeks ago, the field of genealogy has been invigorated by the increasing use of genetic testing to fill in the missing branches of a person’s family tree.  Genealogists are now comparing their Y-chromosomes to those of others with the same surname, to see if a shared surname is also an indication of the shared ancestry.  Within the past few years, surname DNA projects have sprung up all across the world – with hundreds of genetic genealogists digging deep into their genes as they piece together their detailed family trees.

Surnames and Forensics

By far one of the most interesting applications for surname and Y-chromosome comparison is in the field of forensic science.  In 2006, British geneticists found that – for some of the more rare surnames such as Maloy or Rivis, there was a strong connection between surname and Y-chromosome haplogroup.  The authors reasoned that, if DNA were to be recovered from a crime scene, forensic investigators might be able to narrow down the possible perpetrators to a specific subset of surnames.

However, there are several limitations to this idea – namely the fact that most men in the UK have rather common surnames, such as Smith, Green, and Adams.  Men with these surnames have a wide range of Y-chromosome DNA types, so it would nearly impossible for investigators to use the Y-chromosome to locate a suspect.  However, on principle this idea has merit, and further advances along these lines may someday allow investigators to exploit the DNA-surname connection.

One final note: 23andMe customers need not worry that their data will be used in this way — our research database does not include surnames and our terms of service do not allow us to share data with law enforcement unless we are legally compelled to. And even if such a situation did arise, we have publicly committed to resisting legal requests for customer data.

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The opening bars of “Who are You” crash through the speakers, the credits roll and the lead actors of “CSI” pull up at the crime scene to investigate yet another murder.

Since “CSI” premiered in 2000, the show, its spin-offs and imitators have hammered home the idea that a person’s genetic material can readily establish his or her presence at a crime scene. The programs’ popularity has even led to the “CSI effect,” where real juries have come to expect that such information is part of the evidence provided at all trials.

But reality is rarely as simple as TV. According to the President’s DNA Initiative, DNA labs across the country saw a 73% increase in their casework from 1997 to 2000, while their backlog was nearly double that figure. One contributor to lab backlogs: samples containing more than one source of DNA. Picking out each individual from such mixed samples can be extraordinarily costly and time-consuming.

Researchers from the Translational Genomics Research Institute (TGen) and the University of California at Los Angeles have developed a new way to detect whether a specific individual’s DNA is part of a mixed sample, even when that person’s genetic material makes up as little as one one-thousandth of the total. As detailed in PLoS Genetics, this method developed by Nils Homer and his colleagues could help forensic investigators determine just who was at a crime scene.

“By employing the powers of genomic technology, it is now possible to know with near certainty that a particular individual was at a particular location,” TGen researcher and study author David Craig said in a statement. “Even with only trace amounts of DNA and even if dozens or even hundreds of others were there, too.”

The researchers used high-density SNP arrays, much like those used by 23andMe, to genotype a specific individual, a DNA mixture, and a reference DNA sample. They then used statistical methods to compare the individual to both the DNA mixture under investigation and the reference sample. These statistics allowed them to determine if a person had in fact contributed to the DNA mixture.

The researchers demonstrated the utility of their method by testing it on DNA mixtures composed of anywhere from two to 200 people of Caucasian ethnicity, with each single person contributing as little as one-tenth of a percent of the total sample material.

“It opens up a whole new can of worms of what’s possible to do forensically,” said Stanley Nelson, a UCLA-based co-author of the study (and 23andMe advisor), in a statement. (23andMe was not associated with this research.

The ability to distinguish an individual’s DNA from a mixture also has implications for genome-wide association studies. Such projects require large quantities of genetic information, and genotyping the thousands of individuals participating is a costly process. When researchers try to make the data publicly available for use in other studies, they often pool the information in order to maintain each individual participant’s confidentiality. Homer and his colleagues argue that their technique for picking one individual’s DNA out of a crowd could strip away that pretense of anonymity.

“Our findings make it very clear that such an approach realistically does not conceal identity,” they wrote in their study, suggesting that researchers should confidentially share their data in its entirety instead.

Image from the National Forensic Science Technology Center

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