Among male mice born to moms of the low-nutrition diet, their sperm was dotted with 10 to 30 percent fewer methyl group additions at specific locations on the DNA, perhaps resulting in less gene activity than would be normally expected. The authors say those changes in methyl group additions were likely the cause of diabetes-like symptoms in the mice. And even though the next generation of mice—the grandsons—did not have the same altered markers on their sperm, they were afflicted with the same health problems. Exactly why that happens remains a mystery. “We do not yet understand how they store this epigenetic information as they lose the [methyl group] changes that they received on fertilization,” Radford says. Her team says one explanation might be that some other form of epigenetic information is also being inherited or that perhaps these changes take place so early—when the embryo is just a few cells in size—that the effect is indelible even though the epigenetic “message” itself is lost. Other recent studies have identified on-off DNA changes influenced by parental diet across multiple generations, but some researchers say that the changes might be the result of traditional genetic inheritance rather than an epigenetic effect.