Another reason for paranoia about genetic testing

I'm usually very skeptical of claims that widespread DNA testing will result in bad effects -- "Big Brother" finding out your genotype and discriminating against you, for example. A lot of people are afraid of it, but there has been a lot of unnecessary scaremongering.

But today I read this New Scientist story by Alison Motluk:

Anonymous sperm donor traced on internet
LATE last year, a 15-year-old boy rubbed a swab along the inside of his cheek, popped it into a vial and sent it off to an online genealogy DNA-testing service. But unlike most people who contact the service, he was not interested in sketching the far reaches of his family tree. His mother had conceived using donor sperm and he wanted to track down his genetic father.

Now, that doesn't sound so bad, does it? The biological father must have also submitted his DNA to some genealogy database, which came up as a match, right?


The boy paid $289 for the service. His genetic father had never supplied his DNA to the site, but all that was needed was for someone in the same paternal line to be on file. After nine months of waiting and having agreed to have his contact details available to other clients, the boy was contacted by two men with Y chromosomes closely matching his own. The two did not know each other, but the similarity between their Y chromosomes suggested there was a 50 per cent chance that all three had the same father, grandfather or great-grandfather.
Importantly, the men both had the same last name, albeit with different spellings. This was the vital clue the boy needed to start his search in earnest. Though his donor had been anonymous, his mother had been told the man's date and place of birth and his college degree. Using another online service,, he purchased the names of everyone that had been born in the same place on the same day. Only one man had the surname he was looking for, and within 10 days he had made contact.

The implication is very simple: no one is anonymous. Suppose you let your DNA slip anywhere. Everyone does to the tune of 36 million cells per day, not to mention the occasional lucky sperm. Now if one of your relatives is careless enough to have his name and DNA sequence associated in a public database, then your entire genetic profile may be available to anyone who's interested.

This seems like a pretty simple way to find out the surname of any unknown DNA sample you might have. Most relatively common US surnames already have entries at one or more genealogy registry. If a motivated fifteen-year-old can do it once, the CIA can certainly do it indefinitely many times. All that is needed is for somebody to want to find you.

Better not give them a reason.