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Comment by vasilipupkin | Hacker News Reader

I feel like the author is nitpicking here. 7% of genes didn't change but 7% of genes exhibited different "genetic activity levels" ? What does that mean ? Not being a biologist, it sounds to me that .... genes changed...

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No. They're completely different things. Genes are a cookbook. Gene expression ("activity levels") is cooking. You don't need to rewrite the cookbook every time you want to cook something different, you just pick a different recipe from the book. Gene expression changes all the time. That's how you can have different types of cells even though they all share the same DNA. And that's how your cells can adapt to changing conditions. Including changing your diet. Or spending a year in space.

That's a great explanation -thanks !

The claim being made is that 7% of his DNA changed, not his genes.

A 'gene' is a distinct set of DNA nucleotides. What changed were 7% of his gene's expression levels, across time. Which is not a particularly remarkable finding. If approximately the same 7% of genes changed for most astronauts after x months in space, then that would be more interesting. The 7% change is a n of 1 experiment.

The genes did not change, the expression did.

The blueprints for building a classic Ferrari doesn't change, but depending on the handcraft of each person who touches the car, it changes. Easiest way to explain that.

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