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  • The sweet smell of fruit doesn’t normally send rats running. But when researchers paired

  • the orange-cherry-almondy scent of the chemical acetophenone with a painful electric shock,

  • lab rats quickly learned to fear it. Along the way, extra neurons sprouted in their noses

  • and in the smell-processing center of their brains, making them super-sensitive to the

  • scent.

  • This result isn’t shocking. What is surprising is that the rats' pupsand their pups'

  • pupswere also startled by the smell of acetophenone and had the same extra neurons

  • as their fathers, despite never having been introduced to either their dads or the fruity

  • scent before.

  • But how could the pups have inherited something their fathers learned? Basic genetics tells

  • us that only DNA gets passed along to offspring; characteristics like memories, scars, or giant

  • muscles, can’t get passed on since acquiring them doesn’t alter the genetic code. But

  • it turns out that instilling fear in the rats did trigger genetic changes - not in the DNA

  • sequence itself, but instead, in how that code was read and used in the ratsbodies.

  • In every cell, biological machinery constantly translates DNA into the proteins needed to

  • carry out vital processes. Chemical switches attached to the DNA turn genes on and off

  • or up and down, telling the machinery which proteins to produce and in what quantities.

  • These switches, calledepigenetic tags,” are why a kidney cell looks and acts differently

  • than a skin or nerve cell, even though the two cellsDNA is identical.

  • But the switches in any one cell aren’t set in stone: teaching those rats to fear

  • that fruity smell switched one of their smell-sensing gene into overdrive. Researchers don’t know

  • all the places in the ratsbodies where this switch got flipped, but they know it

  • happened in one key set of cells: the ratssperm cells, which would one day pass along

  • this tweaked genetic material, making the next generation of rats super-sensitive to

  • acetophenone.

  • Rodents aren’t the only creatures demonstrating this weird type of inheritance. In Överkalix,

  • Sweden, boys who suffered through tough winter famines went onto have super-healthy sons,

  • with extremely low risks of heart disease and diabetes. And their sonssons had the

  • same excellent health, living an unbelievable 32 years longer, on average, than the grandsons

  • of boys who hadn’t gone hungry.

  • To be clear, this does not mean we should start starving our kids for the benefit of

  • future generationsscientists don’t even know yet exactly which switches the Swedish

  • famines flipped. While we have been able to connect specific epigenetic changes to health

  • effects in mice, were a long way off from being able to make those connections in humans.

  • That may sound like a bummer, but it’s mostly because we humans don’t live in the well-controlled

  • environment of a laboratory. And for that, we should be grateful.

The sweet smell of fruit doesn’t normally send rats running. But when researchers paired

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Epigenetics: Why Inheritance Is Weirder Than We Thought

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    wehou posted on 2016/12/17
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