Letter: Mitochondria myth?

From Michael Whalley

Philip Cohen, reporting on the man who had inherited mitochondrial DNA from his father, asks whether such inheritance “occurs frequently enough to undermine the many studies that assume these processes do not occur” (22 May, p 14).

The word “assume” seems well chosen. Back in 1996 (28 September, p 64) you published a letter from Jim Cummins of Murdoch University, Perth, Western Australia, who wrote: “Mammalian sperm not only contain mitochondria and mitochondrial DNA, but pass them on to the egg at fertilisation. The only exception to this rule is the giant sperm of the Chinese hamster (and possibly some insectivores)”.

Time and time again I have come across articles in New Scientist in which the myth Cummins condemns is perpetuated. A recent example is Hal Whitehead, who makes the claim in relation to sperm whales (15 May, p 42). I can’t help wondering, as Cohen does, how much research would have to be scrapped if the claim that mitochondrial DNA is inherited only through the female became generally recognised as false.

Philip Cohen writes:

• A lot of work would need to be scrapped if this was proved false. But the bulk of evidence favours the almost exclusive maternal inheritance of mitochondria in mammals, including the discovery of a specific mechanism that destroys male sperm after fertilisation. The case reported in this article, while intriguing, may be very rare, and the rarer paternal inheritance is, the less of a problem it is for biologists who assume maternal inheritance to be the rule.

Howick, Quebec, Canada