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For years, the prevailing wisdom has been that our cells contain genes that are essentially carbon copies of each other. That notion is being dashed by studies painting a different picture — one in which even “normal” cells and tissues accumulate mutations over time. New research out of the Broad Institute of MIT and Harvard has identified mutations in normal tissues throughout the body, including some known to drive cancer. (Flaherty, 6/6)

"These are all normal tissues," says Gad Getz, who runs the lab where Yizhak worked. "They are not cancerous." These tissues are just — you. It turns out you aren't simply a clone of the cells you started with, despite what you may have learned in biology class. "You're just like a big puzzle, with different pieces with different sizes," Getz says. "All of them are very much similar to your original DNA," but you are actually a mosaic of cells with small variations. This finding in itself is intriguing. But it also has implications for detecting cancer. (Harris, 6/6)

High school biology teacher Kelly Chavis knew smartphones were a distraction in her class. But not even her students realized the psychological toll of their devices until an in-class experiment that, of course, was then spreading on social media. For one class period, students used a whiteboard to tally, in real time, every Snapchat, Instagram, text, call or other notification that popped up. Students were told not to respond to avoid generating replies ... and further notifications. (6/7)

Doctors had broken the disheartening news to Rachel Palma, explaining that the lesion on her brain was suspected to be a tumor, and her scans suggested that it was cancerous. Palma, a newlywed entering a new chapter in her life, said she was in shock, unwilling to believe it was true. (Bever, 6/6)

Girls, boys, young men and women, parents: the HPV vaccine helps to prevent cervical, anal, penile, vulvar, throat and esophageal cancers. The news Wednesday that former "Desperate Housewives" actress Marcia Cross may have gotten anal cancer from the human papillomavirus and her husband who had throat cancer about a decade ago, provides a Hollywood health lesson on the importance of the controversial HPV vaccine. (O'Donnell, 6/6)

Dominican government officials released more-detailed autopsy results Thursday for three American tourists who died at adjacent beach resorts owned by the same hotel company during the last week of May. All three victims experienced eerily similar symptoms and internal trauma before their deaths, according to a news release from Dominican authorities. Pathologists said autopsies showed the three had internal hemorrhaging, pulmonary edema and enlarged hearts. (Hernandez, 6/6)

When dog owners go through a stressful period, they’re not alone in feeling the pressure — their dogs feel it too, a new study suggests. Dog owners experiencing long bouts of stress can transfer it to their dogs, scientists report in a study published Thursday in Scientific Reports. The Swedish researchers focused on 58 people who own border collies or Shetland sheepdogs. They examined hair from the dog owners and their dogs, looking at the concentrations of a hormone called cortisol, a chemical released into the bloodstream and absorbed by hair follicles in response to stress. (Rehm, 6/6)

In the 15,000 years that humans and dogs have lived together, dependence and mutual affection have deepened our bond. And science has long established that “emotional contagion” between us and our canine pets is very real. The new study, published Thursday in the journal Scientific Reports, is the first to find that this contagion is not fleeting. It also suggests that a dog owner’s mental well-being shapes the pet’s emotional health in a uniquely powerful way. Much has been made of the health benefits that dogs offer to humans. Our heart rates and blood pressure routinely decline in their presence. Our levels of circulating oxytocin — often referred to as the “love hormone” — rise when we gaze into a dog’s eyes. (Healy, 6/6)

Putting up pictures in our new house last fall, I opted for nails, not tape. My family had just relocated from California to Brooklyn, our fourth move in five years. With so much change, it had been hard to feel settled, but it was my job to try. I wanted to create a sense of stability while my children, then 8 and 11, were still innocent enough to believe that life could be stable. I wanted to create a sense of hope while my husband, Jonathan, was still young enough to start over. (Bergstrom, 6/7)