Hacker News Reader

Comment by maxander | Hacker News Reader

The use of "rewrite" is a bit misleading- what's being altered in this mechanism is an epigenetic tag that sits "on top" of one of the standard DNA bases; that an individual's epigenetics are altered as they go through life is well known. But since the underlying cytosine is (as far as we know) irrevocably bound to this tag, it has to be replaced by a different (but identical) cytosine. Its more like going over your handwriting to hide an errant punctuation mark than "rewriting."

View on HN

Actually, it's been a thing for a while that we know the brain has somatic mutations which cause the DNA to differ from cell to cell. While the epigenetic tags are also affected, it goes beyond attaching tags. The brain literally rewrites its own DNA.

https://www.genomeweb.com/sequencing-technology/single-neuro...

Acquiring somatic mutations is not "rewriting its own DNA", it's just acquiring mutations. You can't replicate a piece of DNA without the chance of a mutation happening. The error rate in humans is about 1e-9 mutations/base, so by the time you've grown a brain you're likely to have a whole bunch of somatic mutations just by chance.

Better link without paywall and with link to actual article

http://neurosciencenews.com/neuron-lineage-genetics-2792/

To me, it sounds more like surgically replacing a fragment of your skin to get rid of a tattoo, then after some time replacing it back again to reapply the tattoo. So not exactly a walk in the park. The article seems to explicitly state that it's quite a fragile and risky operation, and that's actually why it so surprised the scientists:

"[T]he process involves making a cut into DNA, it leaves the DNA somewhat vulnerable to mutations, so most cells use the process sparingly [... Studies suggest that in] mammals' brains [it happens] more than in any other area of the body — and Song’s group wanted to know why all this risky business was going on in such a vulnerable tissue as the brain."

I am not in that field, but have researched into methylation a bit. The way I understood it, is that methylation groups are applied to genes that are to be "muted". Thus, if there are not enough methylation groups available, genes that should not be expressed, are.

Some form of memory storage. Maybe rewiring the firing mechanism based on some input.

Ok, we'll s/rewrite/alter/ the title above.

Very appropriate.

also 2015

Good catch. Added.

Reply on news.ycombinator.com