The study focused on ancestry and hidden fragments of history in our own bodies.
Michael Flores has struggled for years with asthma and finding the right medication to treat it.
"Some doctors say that will help you and it doesn't, and then say that doesn't help, but turns out that's the one that does," he says.
But, what if a genetic code deep inside his body could point doctors right to the drug Flores will respond to?
"We've demonstrated is that on a chromosomal level, ancestry matters not only in risk of disease but in drug response," says Dr. Esteban Burchard at UCSF.
Burchard has been studying asthma in Latino patients for more than a decade. The project was launched by the genetic riddle "Why do patients of Puerto Rican ancestry have the highest statistical rate of asthma among Latinos, while those of Mexican ancestry have the lowest?"
Burchard believes the answer traces back to about 1492 and the first collision of European, African and Native American populations.
"There's a mixing of these populations 500 years ago," he says. "We're seeing the effects on that today."
Burchard and his team at San Francisco General Hospital collected DNA samples from patients who identified themselves as being either fully Mexican or fully Puerto Rican on both sides of their family. Then, they looked deeper to see which genes generations of history had actually left behind.
"You can see Puerto Ricans have more European ancestry and Mexicans have more Native American ancestry than Puerto Ricans," Burchard says. "Then we asked, 'Does ancestry matter in important genes?' For example, we know there are some genes that are causative in asthma. Does it make a difference if you're Euro, African, or Native American in that gene?"
To answer that question, they color-coded sections of the patients' chromosomes by which ancestral group they trace back to. Patients of European descent were statistically more susceptible to asthma, while those who had Native American genes were less so.
"What we demonstrated, at least among Mexicans, in this region of your genome, if you have more native American ancestry, you're protected from asthma," Burchard says.
With new funding from the National Institutes of Health, Burchard and his colleagues are doubling the size of the study. Researchers believe it could soon lead to the identification of genetic bio-markers, alerting doctors not only to a patient's risk factor, but also giving them clues about how to treat them.
Doctor Shannon Thyne runs the pediatric asthma clinic at San Francisco General.
"For example, with main medication used for asthma, albuterol which open lungs, from what we're learning there are different sub grops that may benefit more from using that medication and some that may beneift less," she said.
The study will ultimately include 4,000 patients from the United States, Mexico, and Puerto Rico.