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A Link between Y-STR and Surnames?

Everyone knows that a paternity test can confirm a biological relationship between an alleged father and child, and it is understood that the last name of the two tested parties is irrelevant in the testing. But what if it was found that men who share a common last name, but who are known to be unrelated, might in fact share a common paternal ancestry? Researchers in the UK recently investigated this remarkable notion.

Dr. Turi King and her associates at the University of Leicester recently released findings from a study that explored the relationship between English surnames and Y-STR chromosome types. Y-STR, or Y chromosome Short Tandem Repeats, are DNA markers found on the male-specific Y Chromosome. They are polymorphic; that is, they vary greatly among unrelated males. Y-STRs are passed down through the paternal line through generations with little or no change because recombination (a “genetic reshuffling“) does not occur in the Y chromosome. This allows tracing generations upon generations of males with Y-STR DNA profiling. Y-STR testing is used commonly in forensic investigations to exclude a suspect as a contributor to the biological evidence in a crime, especially in cases such as sexual assault, where female DNA may mask a male DNA contributor. Whenever a suspect cannot be excluded, and it appears to be a “match,” the report must state that he, or any of his paternally related relatives, cannot be excluded as the contributor to the Y-STR DNA profile. Because both surnames and Y-STRs are paternally inherited, the researchers wondered how strong the correlation would be, and what factors affect the correlation.

The researchers recruited 2500 unrelated men, selected randomly across the UK, including a control group that did not share surnames, and sets of men who did share a surname, including known surname spelling variants. Their DNA profiles were collected with simple buccal (cheek) swabs, and the researchers analyzed 9 binary Y-STR haplogroups and a set of 17 micro-STRs profiles. Factors they took into consideration in the analysis included non-paternity, local diversity, genetic drift, number of surname founders, and Y-STR mutations.

Dr. King’s study found that there is a 24% probability that two men who have the same last name also share a common ancestor through that name. If their surname is rare, the chance that they share ancestry raises to 50%. Of course, this research applies only to the UK, so these results do not necessarily follow in other countries. What these results do suggest, however, is a possible link between surname and Y-STR chromosome types, which could be potentially useful in forensic applications where large databases exist. In the future, could forensic investigations predict a suspect’s surname based on the DNA profile alone?

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