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

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.