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Comment by loufe | Hacker News Reader

The article headline is practically fake news. The article isn't very clear on it either. It's not someone's DNA that changes, that would be astounding if all the trillions of cells in your body underwent the same genetic mutations. No, this is a change in epigenetics. The things that change what parts of your DNA are expressed and are much easier to coordinate, change, and adapt in the short-term.

Epigenetics are not that foreign a concept that people should assume the average reader won't understand them or will find it any less amazing.

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I consider myself to be very armchair scientifically literate (zero real applied knowledge but I have consumed just about all of the pop culture created on the subject in the last 30 years).

I have never heard the word epigenetics until now and am still confused about what exactly happened to this guy.

Every gene can have a tag attached to it which prevents the gene from being used to create RNA (the tag is a methyl group, so this is called "methylation"). Since the RNA would then be used as instructions for creating a protein molecule, inactivating a gene by tagging it generally causes the cell to stop producing particular proteins. Since each protein has one or more specific jobs to do in the cell, this causes the behavior of the cell to change. There are a huge number of known proteins (millions maybe? I don't actually know), and a vast potential number of proteins (if you just consider all possible ways of arranging the 20 amino acids into a chain), so there are a vast number of ways that cell behavior can change over time. Indeed, this is how we manage to have different types of tissues at all, including our very complicated immune system with cells that act autonomously to protect against disease.

Also, it's well established that there are plenty of feedback loops here. An active gene can code for the production of a protein that activates or inactivates other genes. There are numerous pathways by which external stimuli can amplify or inhibit all of these feedback loops, so external conditions often result in changes to which genes are tagged.

As you can imagine, the state-space of all of this is immense; far larger than just the number and type of genes that you have. Mapping it all is a vast project that might easily take thousands of years.

The well goes deeper still. Another mode of epigenetic regulation involves histones, the proteins around which DNA is wrapped, and the many ways they can be modified (by methylation, acetylation, ubiquitiylation, sumoylation, etc.). Both DNA methylation and histone modifications modulate how DNA wraps around histones, and thus how readily any given segment can be accessed and transcribed into RNA (and eventually translated into a given protein).

This barely scratches the surface. This process, along with others that modify how DNA is folded, brings certain genes closer together (while moving others farther apart), increasing (or decreasing) the likelihood of all sorts of first, second, and third order (...) interactions between them and their products.

And we've only just begun...

Epigenetics are fascinating. In my D&D headcanon, the reason Drow Elves are so obsessed with spiders is because they picture DNA as a three dimensional web whose spatial arrangement is central to gene expression.

> This well goes deeper still

> This barely scratches the surface. This process, along with others that modify how DNA is folded, brings certain genes closer together (while moving others farther apart), increasing (or decreasing) the likelihood of all sorts of first, second, and third order (...) interactions between them and their products.

> And we've only just begun...

Horribly vague, care to elaborate mathematically or at least provide some study links? The 'DNA folding' you propose begs resolution from some study using quaternions or attractors, or ... ?

I see your username is accurate.

This view that epigenetics is a gene switch is actually pretty misleading at least, and probably just plain wrong, as recent research published this year has shown. It is far more a structural and inheritance guiding factor, as it was conclusively shown that methylated promoters very much do still allow for gene expression, contrary to "popular" belief.

That doesn't surprise me in the least; practically everything in biology has turned out to be more complicated than it first looked.

It has started to come up a lot recently in order to produce the above-like click-bait headlines. Here's my standard copy-pasta quoting myself from when it shows up around here:

Epigenetics. It's the make-file for your genetic source code. Certain conditions can cause certain parts of your genetic code to be uncommented or commented-out within any given cell or set of cells. There are actually a number of different kinds of 'comments' (histone modifications [1]) - each set of marks are particular to a different compiler, in different contexts. And these comments/marks are copied with some fidelity to daughter-cells/children along with a high-fidelty copy of the underlying genetic code itself.

So the genes (DNA) themselves are not being heritably altered, rather the recipe for which gene is produced, when, and where can be subtly changed. But again, the same mechanisms that permit the change in expression of those genes during a lifetime (of an organism, or a cell) can be subsequently changed in the next just as easily.

In this way you can store the code for some trait or capability over many generations without having it always be running. It can manifest itself in individual organisms or cells as having very different phenotypes even while possessing the same underlying genetic code.

[1] https://en.wikipedia.org/wiki/Histone_code

It's arguably much closer to RAM than a make file.

Picture a Glucose detector wrapped around a DNA segment that encodes something to break down Glucose. If you zero Glucose inside the nucleus you stop producing stuff to deal with it.

The difference for this analogy is cells never stop compiling. On the other hand if you think of cell division as a reboot it's a better fit.

Your epigenetic state very much starts off inherited from your parents. Also, it's not just a gene switch, and in fact that probably is it's least relevant role, if any. Rather, and besides being a hereditary factor, it determines the structure/packing of your nucleosomes, and therefore determines the integrity of your cell as a whole, not just your gene expression levels.

Thanks for the analogy, I’m actually copying & pasting for future references ;)

Epigenetics is the idea that genes can express themselves differently based on the environment they are put in.

It is how you can have the same genetic code in your brain as you skin, but the cells the genes are part of are completely different.

It's how you can have a hard drive with a ton of information on it, but choose to read only small portions at a time

Genes are the data, epigenetics talks about the program instructions, notably proteins called transcription factors. The latter are of course also encoded for in genes.

The similarities to Von Neumann architecture are .. unsettling.

You might enjoy reading Seveneves

Great book, another rec here too!

Youtube's SciShow gave me my introduction to epigenetics.

Perhaps the science has advanced since this video was created, but I think it is a fine primer on the subject.

https://www.youtube.com/watch?v=kp1bZEUgqVI

I know about epigenetics because of many articles in Popular Science or Discovery.

Ok, that explains a lot, because my imagination was going wild with these 2 things:

According to the article: Preliminary results from NASA's Twins Study reveal that 7% of astronaut Scott Kelly's genes did not return to normal after his return to Earth two years ago.

According to my memory, and now looked it up: Chimps and bonobos in particular take pride of place as our nearest living relatives, sharing approximately 99 percent of our DNA, with gorillas trailing at 98 percent.

Good thing they put a picture in the article of the guy, haha.

> According to my memory, and now looked it up: Chimps and bonobos in particular take pride of place as our nearest living relatives, sharing approximately 99 percent of our DNA, with gorillas trailing at 98 percent.

I thought of that as well while reading about the 7% they mention, but then I assumed they were talking about 7% of the genes that are specific to human kind.

Indeed. If 7% of your genome were replaced with something else, it would be incredibly unlikely that you would still be alive.

Though now that I think about it, if 7% of the human-specific genome was changed, then it must mean that 7% of the rest was changed too. I mean it's not like cosmic particles specifically target human genes, is it?

While I think it’s important to disagree with news that might be less than factual and better yet - think with a skeptical mindset, I think it’s rather anti-intellectual to blanket misleading or factually lacking news as ‘fake news’.

Good thing he didn't do that!

Exactly, I would expect this person to perhaps have some additional mutations (in his superficial tissues so no body wide mutation of course) due to radiation, or perhaps due to selective pressures working differently on them in 0 G. Also I'd expect expression changes (RNA quantity changes), also related to 0 G or maybe to his diet. Also, it is often claimed that chimp DNA is only 1% different from ours. Which is also bull of course, it depends, (as here) on how difference is defined. The telomere story is interesting but from the text it sounds like we already expect that from radiation and calorie restriction.

> would be astounding if all the trillions of cells in your body underwent the same genetic mutations.

spoiler: they won't all undergo the same epigenetic changes either.

Are you sure? Might there be a coordination mechanism of sorts?

I think the issue for the article is that identical twins are not epigenentically identical to begin with, time in space and life in general will only tend to magnify that. In essence, the headline is doubly misleading.

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