Recent studies have shown that in some cases, fathers also pass on mitochondrial DNA. It began with studies of a 4-year-old boy who presented with fatigue, muscle pain and muscle weakness. Suspecting there might be some defects in the child’s maternal mitochondria, researchers looked for abnormalities, which they did not find. They did find that the child had mitochondria from both parents. Subsequently, they also found biparental mitochondria in four other family members in several generations. They found that at least four people across multiple generations in the boy’s family have significant levels of biparental mitochondrial DNA. They also found multiple members in two other families who also had biparental mitochondrial DNA. According to the authors of the study published recently in PNAS, this discovery may help the development of new treatments for devastating mitochondrial disorders, which currently can be treated but not “cured” per se. More tomorrow.