Days before she ended her pregnancy, Joselin Linder, pictured above, was thrilled to imagine herself as a parent. She was 37, newly-married, and though her baby-to-be wasn’t planned, it was soon deeply desired. “Maybe it’s that I played with dolls until I was so old I had to play with them in my closet,” she says. “But it seemed inevitable that I would one day be a mother.”

Linder is not a mother today, more than a year later, because she had an abortion at 10 weeks. She still wanted the child—wanted to call it George, perhaps—but she feared she would pass along the disease that killed her father in mid-life, practically fusing his organs and ballooning his body. She and her sister Hilary inherited the same unnamed illness, but as with most of the thousands of inheritable diseases known to science, there is no cure—except for stopping the affected bloodline.

It’s an agonizing form of prevention the Linder sisters have turned to four times combined. They’ve had three abortions, and in 2009, Hilary and her husband paid $20,000 out of pocket for a round of in vitro fertilization aimed at creating an unaffected embryo. The gene has killed five people in the Linder family, and it now threatens the sisters themselves. But if they have their way, it will die out in their generation.

“I think that’s a big deal,” says Joselin, who lives in Brooklyn, N.Y. “I think we’ve done something amazing with this particular gene.”

The Linders’ story is personal, of course, but it’s also a public milestone. It’s the first known example of genetic medicine not only identifying a deadly new mutation—akin to the next Huntington’s or Cystic Fibrosis—but of a family banding together to stop a disease before it cuts a path through society itself. It illustrates the promise of genomic medicine, which may one day stop disease as we know it, but also the soul-troubling questions that arise when people have a hand in their own evolution.

America is experiencing a boom in biological fortune-telling. Doctors can now scan the genes of a fetus using only a drop of the mother’s blood, testing for hundreds of known mutations, including Down syndrome. Soon they’ll be able to detect a growing list of rare mutations—almost none of them treatable—and predict an embryo’s risk of more common ailments like diabetes, cancer, and heart disease. By that point, millions of pregnant women will be offered a God-like view of their child-to-be and a decision much like the Linders, a decision as miraculous as it is unnerving: When is a life worth living?

“No one has ever recognized a disease quite like this one. It could truly be one in a million, one in a billion.”

“The family gene,” as Joselin calls it, surfaced in the late 1980s, when her father William came home from a family trip complaining of swollen legs and strange fatigue. He waved it off as jet lag, but the swelling spread and the fatigue deepened. He was 40, vibrant and fit, a busy doctor in Columbus, Ohio. But within a couple years he was forced into semi-retirement, hardly able to take the stairs.

“I’m very, very sick,” he told Joselin, who was then 17, and surprised to see her father start to cry. In the years that followed, his body filled with a creamy white fluid, which doctors pumped out by the liter. He got rounder, but lighter, his muscles withering even as something in his belly grew.

He moved into Brigham and Women’s Hospital, a Harvard-affiliated facility in Boston, where he confounded some of the country’s best doctors. In his records, which Joselin shared with NBC News, a series of gobsmacked specialists noted “puzzling results…an occult malignancy…something brewing.” None could come up with a diagnosis, however, let alone a cure.

William Linder died a medical mystery in September of 1996, his autopsy revealing a body both starved and bloated. The cause of death was officially “unknown.” His daughters visited him often, right to the end, shuffling ICU visits into their college schedules. They never suspected that they were getting a preview of their own genetic destiny.

But during their father’s decline one relative managed to track down some files from the National Institutes of Health, the charts of another person who died as their father did: his uncle. That got the family talking and thinking, remembering how past generations had died. At the same time, amid the procession of white coats, a more regular presence appeared: Dr. Christine Seidman, a Harvard professor of genetics.

“Call me Kricket,” she told the Linders.

What if the first carriers of every disease knew it and chose not to pass it on? Would we have Cystic Fibrosis or Huntington’s? Would we even have disease as we know it?

Dr. Seidman’s specialty is the heart, the only organ that “makes music,” as she likes to say, and she wanted to look at William Linder’s heart murmur. She’s director of the Cardiovascular Genetics Center at Brigham and Women’s Hospital, and she thought the murmur might be traced to a gene mutation. By identifying it, she hoped to discover something new about the dance between different bodily systems—and she did.

The Seidman Lab, which helped identify the gene that causes sudden death heart attacks in young athletes, found a “lightning strike” in the Linders’ genes as well. It’s the equivalent of a one-letter typo in the Bible, a single-gene error that seemed to cause the heart murmur, as well as the creamy fluid, and a grim litany of other symptoms. Some of William Linder’s veins were squeezed nearly shut by swelling. Others took on the extra blood, stretched to the edge of bursting.

At first Dr. Seidman assumed there would be other cases like this one out there. She combed through the medical literature. She called Dr. Victor McKusick, the late founding author and editor of “Mendelian Inheritance in Man,” an encyclopedia of heritable diseases. Nothing matched. “No one has ever recognized a disease quite like this one,” she realized. “It could truly be one in a million, one in a billion.”

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Joselin's father, Billy Linder, left, is seen here with his brother Norman and mother Mae Fuhrman in this family portrait taken in the early 1950s. All three died from the same unidentified, incurable genetic disorder that Joselin and her sister suffer from today. Jim Seida / NBC News

With cooperation from far-flung members of the Linder family, who flew to Boston to give blood samples, Dr. Seidman and colleagues charted all the carriers and tracked the mutation back to a “founder”: Joselin’s great-grandmother, Mae. She seems to have developed the mutation spontaneously, at the moment of her own conception, and died of the disease at age 51.

It’s possible that Mae inherited the disease from her mother, Esther, who, according to family lore, developed swollen legs after hanging laundry one winter on a rooftop in Brooklyn. But either way the discovery of such a recent founder was profound. Ancestors double every generation. Some scientists believe that everyone on Earth had a common ancestor as recently as 1,000 years ago.

A genetic disease can spread very quickly, in other words. A “young” genetic disease is one that’s 60 or 70 generations old. The Linder mutation was at most five generations old.

“We’re learning things about our biology that are going to give us the power to make intentional and serious changes to our species,” said Hank Greely, director of the Center of Law and the Biosciences at Stanford University.

The discovery gave the Linder family an unusual opportunity. If they were the only family with the disease, and they knew who carried it, they had the chance to attempt a forever fix. They could stamp out a genetic killer before it spread in the gene pool. “It points to the future,” says Dr. Seidman.

The genome defines us as a species, shapes us as individuals, and through its idiosyncrasies—the random deletions, additions and mutations in each of our cells—exerts a profound influence on the way we live and die. Knowing this, geneticists have begun to look back in time to find the origin of the genes that cause much of the world’s disease. They’ve traced a heightened risk for breast cancer back to a woman in 16th century Iceland; found the same for colon cancer in a man in 17th century England; and walked sickle cell anemia back to 18th century Africa.

The tantalizing question is, what if science could have been there at the founding? What if the first carriers of every disease knew it and chose not to pass it on? Would we have Cystic Fibrosis or Huntington’s? Would we even have disease as we know it? And given what we know now, will science one day be able to eradicate all but a baseline of genetic illness?

“It’s a very cool, very sci-fi, theoretically correct idea,” says Dr. Robert C. Green, a Harvard University geneticist not involved with the Linders’ case. “We’re learning things about our biology that are going to give us the power to make intentional and serious changes to our species,” adds Hank Greely, director of the Center of Law and the Biosciences at Stanford University. “It’s going to be fascinating, and more than a bit scary, to see what we do with that power.”

It's already becoming a controversy. “Since Roe v. Wade, people have assumed that women can have an abortion for any reason prior to viability, but the courts have never directly addressed the issue,” according to Jaime S. King, a professor of law at the University of California, Hastings. As she put it in a recent essay, “the question of whether a woman’s reason matters is upon us.”

Americans United for Life, perhaps the most powerful right-to-life legal organization in the country, calls abortions on the basis of genetic testing “a chilling slide toward eugenics,” and its activists hope to halt that slide at the state level. Last fall they succeeded in North Dakota, which became the first state to ban abortions on the basis of “any defect, disease or disorder that is inherited genetically.” Now the fight is spreading: Missouri, Indiana, and Colorado have recently debated similar bans. And Virginia nearly succeeding in becoming the first state to bar Medicaid from covering abortions based on genetic illness.

“AUL’s goal for children with genetic diseases is the same as our goal for all other children,” Ovid M. Lamontagne, general counsel at Americans United for Life, wrote in an email. “We celebrate the value innate in all human life.”

"These laws wholly disrespect the doctor-patient relationship," Julie Rikelman, litigation director for the pro-choice Center for Reproductive Rigths countered in an email. Last summer, on behalf of the only abortion clinic in North Dakota, Rikelman's organization sued to block the North Dakota law, calling it an unconstitutional "license to question" women's private thoughts. The clinic later asked CRR to drop the case, however, and shift its focus to North Dakota's more sweeping ban on abortions as early as six weeks. Today, as a result, any doctor who helps a local family like the Linders faces up to a year in prison.

As scientists uncover more about genetic destiny, parents could feel pressured to upgrade their genome along with their smart phones.

The Linder sisters are sharing their story for the first time, because they hope to spread awareness of genetic disease in general, and draw attention to their own deepening sickness in particular. But at a time when religious conservatives, techno-skeptics, and old guard right-to-lifers have launched a new effort to stem the spread of genetic science, they also see the need to speak up for the technologies that have gotten them this far.

“It’s genetics, not eugenics,” says Joselin, pushing back against the e-world favored by critics.

Hilary, the older sister, married first and used money from her father’s estate to pay for “pre-implantation genetic diagnosis,” a form of IVF where embryos can be tested for disease and only the healthy ones implanted. PGD is almost three decades old, widely offered, and for years it’s been generally accepted. The result for Hilary was twins, now five years old.

Joselin's father, Billy Linder, left, with his daughters, Joselin and Hillary. All three have the same unidentified, incurable genetic disorder. Billy died in his 40s. Courtesy Joselin Linder

But opposition to PGD is growing as well. Few people would fault a couple for using PGD to guard against miscarriage or to prevent a fatal childhood disease, and only the hardest of hardliners still fight the destruction of embryos that often results when life is created in a petri dish. But many more people balk at selecting out non-lethal diseases, like deafness. Or the mere risk of disease, like breast cancer. Or adult-onset diseases like the Linder mutation.

In Scientific American last fall, Osagie K. Obasogie, a fellow at the Center for Genetics and Society, called the doctors who facilitate such tweaks “the new eugenicists,” and he warned that as scientists uncover more about genetic destiny, parents could feel pressured to upgrade their genome along with their smart phones. Hank Greely, the director of the center of Law and Biosciences at Stanford University, shared a similar, albeit less critical, view in an interview, anticipating “the end of sex” in America.

“It’s going to happen,” he predicted. In 20 years, or maybe 40 years, “most babies in the United States could be conceived using in-vitro with genetic selection, so parents could choose the embryo with the genes they most want to see.”

Joselin recalls confronting this slippery-slope scenario herself on a visit to Dr. Seidman’s office around the time of her sisters PGD. “So we’ll cure it!” she said. “We’ll weed it out from humanity and cure it!” The doctor, who says she merely informs her patients of their options, rather than advise them of a particular path, was quiet for a moment. “Why stop there,” she said finally. “You’re full of bad genes. Which other ones shall we weed out? Acne? Freckles?”

Neither of the Linder sisters look sick, but they’ve both been told they have “a ticking time bomb” inside them.

The Linders, for their part, are sympathetic to some of the criticism. “I don’t think it’s right to select for handsome, blue-eyed babies,” says Hilary. “But if you can save a life? How wonderful that is.” Joselin wholeheartedly agrees.

She is firmly pro-choice, even as she recognizes the complications that come with being so free to choose. She regrets her own abortion. She wishes she had taken a chance with the baby. She didn’t even get to find out if she had lost the genetic coin-toss. Her offspring’s genetic test was scheduled for the same week that Superstorm Sandy pushed the East River into her hospital, closing it indefinitely and throwing Joselin into a state of emotional triage.

The pregnancy was high-risk. Doctors had given Joselin a one-in-four chance of surviving childbirth, because of complications related to the family gene. At the same time, there was talk of a surgery she could have, a procedure that might open up a key vein, relieving pressure elsewhere, and making childbearing safer for her. Meanwhile, as she mulled these variables, along with a storm that felt like “a middle finger from the universe,” the fetus was getting bigger and she felt she needed to act.

Six months later, the surgery failed, and her condition worsened. Neither of the Linder sisters look sick, but their bodies have begun to bewilder doctors much as their father’s did. They’ve both been told they have “a ticking time bomb” inside them. They both have swelling, and the overtaxed veins that result. The nights are the worst, Hilary says, a time when the risk of a burst is greatest. Though her kids just turned 5, she’s already taught them how to dial 911.

Joselin Linder is a 38-year-old humor writer in Brooklyn, suffering from what she lightly calls 'the family gene.' One of its manifestations, seen here, is chronic swelling of her right leg. Jim Seida / NBC News

It wasn’t supposed to be this way. As female carriers of an X-linked disease, the sisters expected to get a relatively light version, with their second X chromosome balancing the defective one. Their grandmother passed the gene to two sons, both of whom died, but she is now 90, and for decades she has told the girls not to worry, “you’ll be as sick as I am.”

Instead the gene confounded expectations again. “I’m scared to death that I won’t be able to see my kids grow up,” Hilary says by phone from her home in Columbus, Ohio. “It’s a slow, painful death,” adds Joselin, sitting at a picnic table in Brooklyn’s Prospect Park, a binder of gruesome family medical documents at her side. They’re hoping they can head it off by going public. They’re hoping another family will come forward, surprising them with the same mutation, and perhaps inspiring an idea for treatment.

Dr. Seidman is currently looking for ways she might be able to “intervene,” if not correcting the mutation, then at least muting its effects. And if not? Well, the sisters will keep hoping, says Joselin. “Maybe I’ll hope a little bit for the discovery of that alien planet where my specific genetic mutation helps me to digest ice cream like brussels sprouts,” she jokes.

“It’s got to be out there. After all, the universe, like the human body, is vast and completely out of our realm of understanding.”