A mysterious loophole linked to the mitochondrial DNA might have the answer to why women live longer than their male counterparts.
The mitochondria, which are called the "powerhouses of the cell" comprises of DNA which is different from the nuclear DNA. The mitochondrial DNA is inherited from the mother to the child without any contribution from the dad.
AdvertisementAccording to a new study published in the journal Current Biology this direct line of mitochondrial inheritance may allow harmful mutations to accumulate.
Natural selection normally ensures that harmful mutations are kept to the barest minimum by not passing it down to future generations.According to study researcher Damian Dowling, evolutionary biologist, Monash Univeristy, Australia, the mitochondrial DNA mutations, that are usually harmless to females, pass through the gates of natural selection and find their way to the next generation.††††††††††† This usually results in a lot of mutations, that are harmful to the males and affect their longevity, but which are harmles to women.
The phenomenon, nicknamed "mother's curse", was tested on the fruit fly drosophila melanogaster. It has always been believed that women outlive men because they take lesser risks than men during life's journey and also because the male hormone testosterone is linked to reduced longevity.But insects have no testosterone and are not prone to take risks like humans, so it was prudent to start this particular study with them.
Mitochondrial DNA was taken from thirteen different fruit fly populations from around the world and inserted into another group of flies with the same cellular DNA. This made sure that in these flies only the mitochondrial DNA differed.
It was found that in all the strains of flies studied, the males suffered in terms of ageing and longevity while the female parameters did not suffer in any way. This observation provides strong evidence that the mitochondrial genome is riddled with loads of deleterious mutations that affect male aging but does not harm females.
The inheritance of the mitochondrial DNA occurs in the same manner in all species and therefore, this finding is expected to be true of humans too.However, despite this gloomy note, all may not be lost for men as Dowling and her colleagues are now seeking to uncover the genes in the nuclear DNA of men that may actually compensate for their mitochondrial handicap.