The "Mother's Curse"—an evolutionary "loophole" that exempts some harmful DNA mutations from natural selection—may explain why women tend to live longer than men, according to Australian researchers.
The theory behind the 'Mother's Curse'
The "Mother's Curse" theory focuses on the inheritance of mitochondrial DNA. Unlike DNA that resides in cell nuclei, mitochondrial DNA lies in the energy-generating components of cells and is inherited directly from the mother, with no input from the father.
This direct line of mitochondrial DNA inheritance can facilitate the accumulation of mutations that are harmful to men but not women because mutations are less likely to be weeded out of the gene pool through natural selection.
According to evolutionary biologist Damian Dowling and his colleagues at Monash University in Australia, the accumulation of those mutations may contribute to reduced life expectancy among men.
Putting the theory to test
Dowling and his colleagues tested their hypothesis in fruit flies. They took flies with the same cellular DNA and inserted mitochondrial DNA from 13 different fruit-fly populations across the globe.
The study—published in Cell Biology—found that the average life expectancy among males varied significantly. However, there was less variation among the female flies.
Dawling says that the findings provide "strong evidence that there are lots of mutations within the mitochondrial genome that are having an effect on male aging, but are having no effect whatsoever on female aging."
Cellular DNA may help men overcome mitochondrial DNA mutations
"In some ways, this is bad news for medical biologists, because we're not looking for the mutation that causes early male aging, we're actually dealing with a whole lot of mutations within this genome that are teaming up to shorten male life span," Dowling says.
However, researchers speculate that certain genes in cellular DNA may be helping men counteract the damage that mitochondrial DNA is causing. "We're looking to uncover those genes now," Dowling says (Pappas, Live Science, 8/2; Dallas, HealthDay, 8/2; Monash University release, 8/3).
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Daily roundup: Aug. 3, 2012