Welcome to the world of preventative DNA mapping.

Dan, a 39-year-old programmer, knew his family had a history of a genetic defect called BRCA1, which drastically increases the chances of contracting some forms of cancer. He was worried he carried the defect, but was reluctant to have his DNA checked for it. He felt it might be easier to live with the uncertainty than learn he was at risk. “Every little ache and pain would suddenly have me at the doctor, begging for detailed tests,” he says.

An artistic representation of DNA. | 162843/Imgur

Then, during a routine doctor visit, Dan mentioned his family history of BRCA1. His doctor said he could easily test for it with the blood he’d already drawn. In a snap decision, Dan said yes, “like I was on autopilot.” When the test results came back, Dan’s doctor told him he did not have the defect.

Now Dan is considering having his entire genome mapped.

In genome sequencing, researchers build a map of our DNA — 3 billion “base pairs” of nucleotides, which are organized into groups called genes. We get one copy of most genes from our mother, and another from our father. A mutation occurs when there is an error in copying a parent’s gene to our DNA. Many mutations are beneficial and are what allow us to evolve. Some are harmful, so mappers look for mutations that put us at risk of disease. A dominant mutation requires only one gene for its effects to manifest. A recessive mutation requires a copy from each parent. So if your mother and father both gave you a recessive gene for sickle-cell anemia, you might get it. If you received a dominant mutation for cystic fibrosis from your mother, that’s all you would need to risk contracting it.

Genome mapping is already common for cancer patients or parents of a sick child, because it can help predict future birth defects or aid cancer treatment.

“Genes often predict how well these individuals respond to various chemotherapies — which drugs will work best for you versus me, and which will give each of us the worst side effects. Parents who have children born with medical problems frequently seek whether a mutation is the culprit — so that they can screen for it, and prevent a subsequent child from having it.”
—Dr. Robert Klitzman, Columbia University

But now, more and more healthy people are interested in having their DNA sequence mapped out. One factor is reduced cost.

The first human genome was mapped in April 2003, under the Human Genome Project. That map took ten years to complete and cost $2.7 billion dollars. Today, the cost is around $2,900, and ads for genome mapping run in the breaks for “Rick and Morty” on Hulu. Suddenly, the technology is within the grasp of many Americans. Many people have their genome sequenced out of personal or scientific curiosity — or to determine if they or their future children are at risk of certain diseases.

“I’m a healthy 28-year-old woman, but some nasty diseases run in my family: coronary heart disease, rheumatoid arthritis, Alzheimer’s and breast cancer. So I decided to read the tea leaves of my DNA. I reasoned that it was worth learning painful information if it might help me avert future illness.”
Kira Peikoff, New York Times

The US government supports getting as many people sequenced as possible. In fact, it’s a national priority. President Barack Obama launched the Precision Medicine Initiative in January 2015. It aims to get one million Americans to volunteer for genome mapping, so scientists can study thousands of healthy and sick people and figure out the genetic variations behind a multitude of diseases like autism and diabetes. In what some are calling the “genomic revolution,” medicine is moving from the population-based approach we have now, to more personalized medicine based on each patient’s genetic makeup.

“Most medical treatments have been designed for the ‘average patient.’ As a result of this ‘one-size-fits-all-approach,’ treatments can be very successful for some patients but not for others.”

The more genomes that are mapped, the faster that can happen, which is one reason scientist Stephane Budel and his wife decided to fork out $2,900 each.

“We wanted to contribute to the genomic revolution. Just like the internet, the value in genomics resides in the number of its participants, and the value of each individual genome increases as we sequence (and make sense of) more genomes.”
—Stephane Budel, scientist

If you’re considering genome sequencing, keep in mind that the genomic revolution is still in its early days. Your results may not provide you with any evidence that justifies treatment or changing your lifestyle. Only 1 to 2% of subjects actually exhibit any “actionable” result, Harvard geneticist Dr. Robert Green told CNBC’s Meg Tirrell before she had her DNA mapped.

There’s even debate over whether that 1 or 2% can be helped based on what geneticists find.

“Because genome sequencing is so young, we only have a decade and a half of historical data from which to draw conclusions. Our understanding of all the implications of our genetics hasn’t caught up yet to the power of sequencing technology.”
Meg Tirrell, CNBC

To prove the point, Green told Tirrell some 20% of people exhibit a dominant mutation, but show no signs of the related diseases.

A scientific model of a strand of DNA. | Imgur

It’s also important to realize that the sequence won’t give you a comprehensive account of everything that’s hiding in your genome. It’s more of a bird’s-eye-view. If your geneticist is concerned about a particular genetic condition, they’ll still have to run a specific test for it. “All of the data is there,” says Dan, the programmer who impulsively had his bloodwork tested for BRCA1. “But we’ll still only find whatever someone is looking for.”

Dan believes that computing power promises to make genome mapping more medically useful. “Corporations have been perfecting data-mining techniques for years, mostly for marketing purposes and risk assessment,” he says. “But those same concepts could be applied by creating profiles for genetic problems.”

You should do your research when assessing any company’s claims that their genetic mapping service can provide information that’s of actionable, medical use to you. The Food and Drug Administration (FDA) in November 2013 banned 23andme from selling its DNA testing product, which was far less comprehensive than a genome sequence, because the company couldn’t back up claims the tests were of medical benefit. 23andme is selling its tests again, but they’re much more limited in scope—only informing patients whether they are carriers of 36 diseases that could be passed on to their children.

Some potential subjects also have privacy concerns about uploading their genetic data to a computer server. “It’s the reality of our age that no information remains private,” says Dan. “Some government, corporation or hacker will eventually get it.”

There are federal laws that prevent employers and health insurers from discriminating based on genetic data. But there are no similar protections in place for life, disability or long-term care insurance.

So if you’ve been watching ads on Hulu and wondering if genome sequencing will prolong your life or prevent your kids from having birth defects, the reality is the tests may be inconclusive. But it’s certain that the addition of your genetic information to the pile will help scientists figure out ways to make all of us healthier in the decades to come.