Maternal Inheritance of Mitochondria

As discussed previously, the mitochondrial theory of ageing rests on the observation that mitochondrial DNA is exposed to high levels of reactive oxygen species when the mitochondrion is performing its redox chemistry. These reactive oxygen species cause mutation. These mutations accumulate, gradually damaging the mitochondrion s ability to function. This happens in 

As far as the mitochondria go, the most significant difference between the male and female is that the male mitochondria have to produce a lot of ATP to propel the sperm as quickly as possible towards the egg, and the female mitochondria do not really have to do much at all. If free radicals generated by an active electron transport chain are responsible for damage to mitochondrial DNA, then it is reasonable to assume that sperm mitochondria are likely to be more damaged than those in the egg. To take this idea one step further, perhaps the mitochondria in the egg cells are prevented from carrying out oxidative phosphorylation at all, in order to preserve as accurate a copy as possible of the DNA to pass to the offspring. 

In the systems that have been studied, it can be seen that cells destined to become the female germ line are identified and set aside very early in development. In the female, these cells will go on to form the eggs, and will contain the mitochondria that will pass to the next generation. When one of these eggs is fertilised, the cells that will form the gametes for the next generation are set aside, and so on. 

Carol A. Allen, Mark van der Giezen and John F. Allen 

From these observations, it is possible to see how mitochondria could be passed from one generation to the next without ever having to fulfil their role as generators of cellular energy, but only having to act as templates. The energy for replication could come from the egg s helper cells, and once any mitochondria have an active respiratory chain they become unsuitable to act as a template for future generations (Fig. 3.5). If such mitochondria did get 

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