Male adoptees are using consumer DNA tests to predict the surnames carried by their biological fathers.

They are using the fact that men who share a surname sometimes have genetic likenesses too.

By searching DNA databases for other males with genetic markers matching their own, adoptees can check if these men also share a last name.

This can provide the likely surname of an adoptee's biological father.

The genetic similarities between men who share surnames occur on the Y chromosome, a package of genetic material passed on, more or less unchanged, from father to son - just like a last name.

Because of this pattern of inheritance, men with the same surname may also share a similar complement of genetic markers on the Y chromosome.

At least 30 men registered with US consumer genetic testing firm Family Tree DNA have found their "biological surname" in this way, the company's chief executive told BBC News. The company has an online database called Ysearch containing genetic information from 125,000 men, along with surnames and other genealogical data.

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