BOSTON — It used to be that the science of genetics - the study of all those double helixes of DNA - thrived only in the realm of bleached lab coats and dry scientific journals. But not anymore.
DNA has gone decidedly mainstream. Today, the people who grapple with this subject - one that probes the molecules that hold the very blueprint for organic life - come from law offices and police stations, fertility clinics and jury boxes.
Moreover, the growing reach of DNA is forcing ordinary citizens to confront the double-edged nature of genetic science. Indeed, the wider application of DNA research is raising a host of concerns, from tough privacy issues to questions about the dangers of predicting that offspring of certain parents will be predisposed to disease.
"It shows enormous promise for human benefit, but in almost every instance it can also be a tool for questionable or immoral behavior," says Mark Hanson, an associate at The Hastings Center, a bioethics think tank in Garrison, N.Y. "It's a double-edged sword in just about any application you can think of."
On the positive side, DNA research is an aid in a growing number of arenas.
* Its use as a crime-fighting tool is skyrocketing. The FBI's new nationwide DNA database will help catch criminals on the basis of a few strands of hair or drops of sweat they leave behind.
* It's helping to set free those wrongly convicted of crimes, including a handful of death-row inmates.
* It's helping moms determine, with little doubt, the identity of their children's father, thus lowering the number of paternity suits.
A case in Chicago dramatically illustrates the promise of DNA.
In the days after the August rape and murder of a young girl, police charged two boys, ages 7 and 8, with the crime, making national headlines. But their case fell apart and languished for months.
Then a DNA test of evidence at the scene made a near-match to a convict named Eddie Durr. Police suspected a close relative of Mr. Durr's had committed the crime. His brother gave a DNA sample and is now charged with the crime, as well as with two other rapes.
Why police waited so long to test the evidence isn't clear - and may point to the time and expense that DNA testing requires. But in the end, DNA was the main clue to finding a new suspect.
Indeed, Florida tops US states with 155 "cold hits" from its database in cases where police had no other leads.
A match made in ... the lab
FBI officials expect more matches like these, now that the DNA databases of all 50 states are being linked. The move, announced last week, mimics a database in Great Britain. Since going online in 1995, the British DNA files have matched 28,000 people to crime scenes.
But Britain has few of the civil-rights safeguards enshrined in the United States Constitution. The American database, moreover, has many skeptics.
Currently the database is made up of samples from convicts. Each state decides which crimes - from burglary to rape or murder - qualify an offender to give a blood, saliva, or other sample.
For critics of a DNA database, it's a privacy issue that could someday affect more than just convicts. "It's invading their privacy because they're more likely to commit crimes. If you open that door, why not all men ages 16 to 36? Or all welfare recipients?" says Ruth Hubbard, biology professor emeritus at Harvard University in Cambridge, Mass. Indeed, one British police group is calling for all residents to submit DNA samples.
There's also the possibility that research would be done on the inmates' samples - and lead to discrimination based on people having a kind of "criminal" gene.
But DNA testing is also helping to prove innocence. Some 55 people, including several death-row inmates, have been exonerated with its help. Also, a recent FBI report on prime suspects found that a full 25 percent of those who were DNA-tested had no link to the crime.
In a more unusual application of DNA testing, it has helped Maine state game wardens nab 12 poachers this year. In one case, wardens raided a resident's freezer and found slabs of deer meat. The suspect said it was from a deer he shot legally last year. But DNA tests showed the meat was from two deer. He then admitted to killing a deer this year, illegally.
Yet there's more to DNA testing than solving crimes. Take the fast-growing Houston-based paternity service, Identigene. Its 800 number is advertised on billboards from Los Angeles to Atlanta. For $475, a client can confirm paternity within a week.
The 300 to 400 calls the firm gets each day come from all kinds: fathers who want to be sure a child is biologically theirs before they commit to raising it, adults who have doubts about their parentage, or mothers who want to force a father to pay child support.
DNA testing is encouraging many reluctant fathers to settle out of court. In one Massachusetts county that includes Boston, 3,430 paternity suits were filed in 1996. This year, the total may be half as many.
Hard choices for parents
But in parenting, breakthroughs in DNA research are also causing much debate. Scientists' recent declaration that certain genes may make their bearers - and their offspring - predisposed to anxiety or certain diseases makes for tough decisions, especially for aspiring parents.
If parents have a child - knowing the child is at risk for a disease or bad behavior - are they responsible for the problem? Could they even be charged with child abuse? And should an insurer have to pay for treatment for that child? These are some of the questions on the horizon.
Some couples are glad to know the information, so they can act accordingly. But the ominous part of genetics for some ethicists is the iron-clad description of destiny - medical or behavioral.
"Somehow, concrete information about the kind of person we're predisposed to be runs counter to our sense that our futures are open," says Mr. Hanson of the Hastings Center. "The biological equivalent of damnation of the soul is something people want to resist."