There’s also epigenetics with mechanisms like histone modification and DNA methylation that can control expression without changing the DNA, but still being heritable.
Only the first one is DNA, and only a small portion of 'coding' DNA was initially regarded as important.
My question is how? Structural organization implies information. Who thought "Nah, evolution put that in for shits and giggles"? Was it just things we couldn't observe at all without modern scanning electron micrography?
More to the point, there is still chromosome structure when the cell is normal mode, expressing proteins instead of replicating itself. It's just it is spread apart, probably like a pop-up book where "pages" will snap open and become accessible for transcription as part of gene regulation and other times will be folded up so genes in that section aren't expressed.
Some of the reason it is tough to make GMO products that are really effective is that it's not enough to put a gene in and have it expressed a little, you want to have it expressed a lot. For instance the first version of Golden Rice produced Vitamin A but not enough to matter, it took several years to make one that expressed the genes strongly enough that it made significant amounts of Vitamin A.
> Was it just things we couldn't observe at all without modern scanning electron micrography?
Perhaps also that we couldn't imagine, much less accept, that a dumb semi-random process tweaking bits could, over time, organize those bits into higher level abstract structures. We still mostly talk about evolution mutating genes, where perhaps if you zoom out a little, it's actually working at a higher level of abstraction.
Incidentally, this is the same outlook as some people have today wrt. LLMs - they can't accept the idea that backprop running on a blob of weights representing a simple (if large) graph can start encoding increasingly high-level, abstract organizational structures.
Can't observe and woefully hard to understand. Remember in the 1950's the only genetic disease they could trace to a mutation was sickle cell and that was guesswork. They didn't have any of the cute editing techniques or amplification and sequencing tools. It's a miracle they figured out what they did.
so the thing that makes this complicated is that having non-coding DNA that does nothing for an individual can still be helpful for a population. they essentially serve the same purpose as commented out code that is really common when devs aren't using version control. the comments won't affect the program as it currently exists at all, but they make it so small changes to the code can more easily change the functionality.
Maybe not as much commented as unused. Turns out, there's plenty of that in DNA, and you can force turning it on. See e.g. the bit about snakes growing legs in the video I linked - they still carry the blueprint for legs in their genome, but have it suppressed.
