Deciphering Daddy's DNA
Genetic advances have improved paternity tests
Not so very long ago, fatherhood had a bit of mystery to it. No more. Advances in genetics have made paternity tests one of the simplest and most reliable medical tests ever available. Being able to be 99.99 percent sure has helped fuel the frenzy over the fate of little Dannielynn, the late Anna Nicole Smith's infant daughter, and her four would-be daddies. It also made last week's announcement that DNA samples would be taken from the body of the late soul legend James Brown before burial—to settle new paternity claims—seem almost commonplace.
Far from Hollywood, DNA-based paternity tests are used every day to determine child support and custody or to put a worried mind at ease. "It was a relief," says Mandy, 32, of Kansas, who asked that her last name not be used. Her father had died at age 16 and hadn't told his parents he'd gotten a girl pregnant. A few months ago, Mandy decided she wanted a family medical history for her children, ages 8 and 11. She asked her father's parents, and they said they'd like to do DNA testing first. Last week, she found out that they are indeed her grandparents. "I was scared to death that maybe my mom wasn't honest with me," she says. "It's neat having the confirmation that everything I had been told was in fact the situation."
As DNA technology has become more precise, paternity tests like Mandy's, which could be done without her father's DNA, are becoming cheaper and easier. It's now possible to determine paternity using DNA from cousins or grandparents, or from a discarded coffee cup. Procedures such as amniocentesis can be used to determine paternity well before a baby's birth. And sometime soon, noninvasive tests may be able to ID Dad through bits of fetal DNA floating in a pregnant woman's blood.
Paternity testing first hit the headlines in 1943 when starlet Joan Berry sued Charlie Chaplin, claiming he was the father of her child. A simple blood-type test proved Chaplin could not be the father, but at the time such tests weren't admissible in court, and Chaplin was ordered to pay child support. The case prompted new laws allowing blood tests in paternity cases, but those tests could eliminate just 40 percent of males as the father. In the 1970s, new tests based on variations in white blood cells raised the exclusion rate to 80 percent. DNA testing, which entered the market in the late 1980s, has made paternity testing almost foolproof, raising the accuracy rate to 99.99 percent for the most common tests. Further testing can raise the odds to astronomical levels in contested cases. "The accuracy has greatly increased," says David Gjertson, a professor of biostatistics at the University of California-Los Angeles who helped develop DNA-based paternity tests.
Then there's the CSI approach. Current DNA tests make it possible to use old or degraded DNA samples, such as random cells from a man's razor or even from earwax on a used Q-Tip. Sometimes dental floss tells the tale. In 2002, millionaire Steve Bing alleged that MGM mogul Kirk Kerkorian, then 84, had hired private investigators to go through the trash can outside Bing's home. Bing had been romantically linked with Kerkorian's ex-wife, Lisa Bonder Kerkorian. DNA on dental floss fingered Bing as 4-year-old Kira's father. "You can send us almost anything, and we can get DNA out of it," says Howard Coleman, CEO of Genelex, a genetics-testing lab in Seattle. "Anything that someone's had contact with ... and we can give you a very conclusive answer."
The simplicity of gathering DNA, and the public's growing knowledge that every used soda can tells a story, has increased the opportunity for fraud in paternity cases. Kerkorian's former wife admitted using saliva from one of his grown daughters in an attempt to prove that Kerkorian was Kira's father. State child-support programs, which pay for the bulk of paternity testing, require that the parties being tested appear in person at a designated site in order to establish a "chain of custody."
Chain of custody is also crucial in immigration cases. Increasingly, United States embassies require paternity testing to verify the relationships of people seeking to join family members in the United States. Terry Carmichael, vice president of marketing and sales at Gene Tree in Salt Lake City, says 5 percent of the lab's paternity work involves immigration. Labs that are certified by the international blood bank association AABB follow standards to assure a chain of custody. Still, fraud happens. Men will send a buddy in to give a sample, or a woman will bring in a different child.
Know now. Traditionally, children aren't tested to determine parentage until they are born. But some parents aren't willing to wait. Chorionic villi sampling and amniocentesis, which are used to test fetal DNA for genetic disorders such as Down syndrome, can also be used to identify the baby's father in the first or second trimester. Dawn, who asked that her last name not be used, found herself shopping for prenatal paternity testing after she went through a rough patch in her life, had a one-night stand, and then found out she was pregnant. "My husband was worried that it wasn't his," she says. "I knew it was my husband's baby, but he wanted to be 100 percent sure that it was his, so he could be excited through the pregnancy." The couple found Gene Tree on the Internet, and paid $445 for the test. Dawn's obstetrician agreed to do an amniocentesis, and the sample was compared with those from Dawn and her husband. The baby, to be born this summer, is his. "It would be nicer if it wasn't so expensive," says Dawn, 27, "but it meant more to us to relieve that anxiety and worry."
In 1997, researchers in Hong Kong discovered that bits of DNA from a fetus float freely in the mother's blood throughout pregnancy. Since then, scientists have been hard at work trying to figure out how to use that DNA to devise better tests for genetic disorders like Down syndrome. But companies like Gene Tree are already marketing baby-gender tests based on free fetal DNA, and Carmichael predicts that paternity tests are 18 months away. "It's annoying," Farideh Bischoff, a molecular cytogeneticist and associate professor at Baylor College of Medicine, says of these souped-up versions of "Who's Your Daddy?" that are coming ahead of broader medical applications, the kind she's working to develop.
But people have a way of using science to find out what they really want to know, and Carmichael has no doubt that there will be a market for these paternity tests, too. "We know the answer to the question is very, very important," he says. "We think it will reduce people's anxiety and prepare them for fatherhood."
This story appears in the March 12, 2007 print edition of U.S. News & World Report.