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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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B2 中上級

エピジェネティクス遺伝はなぜ私たちが思っているよりも奇妙なのか (Epigenetics: Why Inheritance Is Weirder Than We Thought)

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    wehou に公開 2021 年 01 月 14 日
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