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Stanford University School of Medicine

Evidence for “mother’s curse” — a quirk of evolution — found in flies

vintage-1319058_1280Quick genetics primer: In nearly all mammals, offspring receive one set of genes from their mother, one set from their father -- even-steven. This genetic material lives in a tiny bubble-like vessel in the cell called the nucleus.

But, here's the twist. There's also a bit of DNA in another spot in the cell called the mitochondria -- an energy-supplying organelle that is thought to have originally been an independent creature swallowed by a cell to provide fuel. Mammal offspring only inherit mitochondrial DNA (mtDNA) from their mothers, as sperm have no mitochondria.

This puts men at a disadvantage, as their mitochondrial DNA is at an evolutionary dead-end. Mutations that harm women are winnowed out, but versions of genes that harm males, but don't affect females, are passed to sons, in a phenomena known as the "mother's curse."

On to the news: A recent study from Vanderbilt University and the Fred Hutchinson Cancer Research Center has bolstered the "mother's curse" hypothesis, which previously had only been confirmed in plants. A Vanderbilt press release explains:

[The researchers] discovered a mtDNA mutant in the fruit fly Drosophila melanogaster that substantiates the mother's curse hypothesis in animals: It reduces male offspring's fertility as they age but does not have any observable effect on female siblings.

'In the 20 years since this possibility was recognized, a few mitochondrial mutants have been reported that have deleterious effects on male offspring,' said Maulik Patel, [PhD] assistant professor of biological sciences at Vanderbilt who headed the study, 'but none of them convincingly showed that the mutants did not have any negative effects on the females. Our study is the first to look comprehensively for possible effects of male-harming mtDNA mutants on females and we were fortunate to find one such mutant that has a negative impact on male offspring without having, as far as we can assess, any adverse effects on the female siblings.'

The research appears in eLife and has implications for the treatment of mitochondrial diseases, a broad group of disorders caused by malfunctioning mitochondria.

Previously: Fast-forwarding evolution to select suitable proteins and Computing our evolution
Image by Jo-B

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