But, while the number of people affected by such mutations is estimated to be between one in 200 and one in 400, mutations do not translate to serious diseases in most cases. Because the harmful changes are often only present in low levels, and because a single cell can contain both mutated and normal mitochondria, it is widely believed that only one person in 5,000 – or even one in 10,000 – will be affected by mitochondrial disease.
线粒体突变可能造成癫痫、肝功能衰竭、糖尿病和心肌病变等严重后果。但预计此类突变影响的人数比例为二百至四百分之一，基因突变在多数情况下不会造成严重的疾病。因为有害变化往往频率很低，还因为单个细胞也可以同时包含突变线粒体和正常线粒体，人们普遍认为只有五千至万分之一的人将受到线粒体疾病的影响。