Hundreds of thousands of people who have been conceived using anonymous donor sperm may track down their biological fathers easier than thought. It seems, however, that this is only the case for boys and not for girls, due to the unique Y-chromosome in males. Only males have this chromosome and so all males inherit their "Y" from their fathers. Think of it as the family surname that is usually inherited only from the father’s side.
Using this piece of information, a 15 year old boy gave his DNA to a genealogy service (FamilyTreeDNA) on the Internet that uses DNA to find their clients’ genealogies. The service didn’t need to have the exact DNA of the father on their database; all they needed was a close DNA match with a particular surname (remember Y-chromosome = surname).
The boy knew from his mother the birth-place and birth-date of his father. Combining that with his biological father’s family name, he used another online service (Omnitrace) to get records of every man born at that place on that day with that surname.
Within 10 days of the asking for the records, the boy had made contact with his biological father.
The full story doesn’t say how the conversation went or what the ending was…
"hello, Mr. X? You don’t know me, but…"