Do you know that women outlive men?
Scientists are beginning to understand one of life's
enduring mysteries -- why women live, on average, longer than men.
Published August 2 in Current Biology, research led by
Monash University, describes how mutations to the DNA of the mitochondria can
account for differences in the life expectancy of males and females.
Mitochondria, which exist in almost all animal cells, are vital for life
because they convert our food into the energy that powers the body.
Dr Damian Dowling and PhD student, Florencia Camus, both
from the Monash School of Biological Sciences, worked with Dr David Clancy from
Lancaster University to uncover differences in longevity and biological aging
across male and female fruit flies that carried mitochondria of different
origins. They found that genetic variation across these mitochondria were
reliable predictors of life expectancy in males, but not in females.
Dr Dowling said the results point to numerous mutations
within mitochondrial DNA that affect how long males live, and the speed at
which they age.
"Intriguingly, these same mutations have no effects
on patterns of aging in females. They only affect males," Dr Dowling said.
"All animals possess mitochondria, and the tendency
for females to outlive males is common to many different species. Our results
therefore suggest that the mitochondrial mutations we have uncovered will
generally cause faster male aging across the animal kingdom."
The researchers said these mutations can be entirely
attributed to a quirk in the way that mitochondrial genes are passed down from
parents to offspring.
"While children receive copies of most of their
genes from both their mothers and fathers, they only receive mitochondrial
genes from their mothers. This means that evolution's quality control process,
known as natural selection, only screens the quality of mitochondrial genes in
mothers," Dr Dowling said.
"If a mitochondrial mutation occurs that harms
fathers, but has no effect on mothers, this mutation will slip through the gaze
of natural selection, unnoticed. Over thousands of generations, many such
mutations have accumulated that harm only males, while leaving females
unscathed."
The study builds on previous findings by Dr Dowling and
his team that investigated the consequences of maternal inheritance of
mitochondria in causing male infertility.
"Together, our research shows that the mitochondria
are hotspots for mutations affecting male health. What we seek to do now is investigate
the genetic mechanisms that males might arm themselves with to nullify the
effects of these harmful mutations and remain healthy," Dr Dowling said.
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