As we age, blood stem cells, the essential source of new blood cells in the body, can accumulate genetic mutations. Now, scientists have not only discovered the mechanism that fuels their unchecked growth but have also found a way to stop it. The study reveals that a common aging-associated mutation in the gene Dnmt3a boosts the power-generating function of mitochondria in blood stem cells. This mutation allows the cells to make copies of themselves more readily than normal and creates fertile ground for the development of clonal hematopoiesis, a condition that dramatically increases the risk of heart disease, blood cancers,...