A few years ago, however, Dr Ames found he could pep up the activity of the mitochondria of elderly rats with positive effects on the animals' memories and general vigour by feeding them two other molecules: acetyl carnitine and lipoic acid.
Beyond the nuclear membrane, in the part of the cell called its cytoplasm, is an array of specialised organelles such as mitochondria (which generate energy) and chloroplasts (which photosynthesise), and also further membranes, known as the endoplasmic reticulum, that carry out a range of tasks from making proteins to disposing of waste.
An embryo whose cells have human nuclei and rabbit mitochondria is not a monster.
Because each cell has lots of mitochondria, but only one nucleus, there is a better chance of getting mitochondrial genes than nuclear genes from a fossil.
Having fewer or less effective mitochondria causes a drop in demand for glucose, and might thus cause a cell to become insulin resistant.Even narrowing the question down like this, though, left 44 genes to look at.
The hyper-specialised descendants of those ancient bacteria, the mitochondria, form the "power plants" inside the cells of all complex life today.Mr Lane's prose is clear.
The resulting partnership was the ancestor of every plant and animal now alive, and the descendants of the enterprising bacterium that co-founded it are known to modern science as mitochondria.
The DNA of the mitochondria is streamlined, and all of it is vital.The mitochondrial DNA carries the code needed to help make 13 proteins, including many of those that form the "electron-transport chain".
If so, it means that the private lives of the mitochondria still hide some intriguing secrets.
The thought that the underlying cause may be hereditary, though, is one reason for disbelieving the hypothesis, which gained traction a few years ago but is now discredited, that measles vaccinations cause autism.One suggestion that does pop up from time to time is that the process which leads to autism involves faulty mitochondria.
In addition to their mitochondria, plants have a second relic symbiont, the chloroplast.
