> But it remains true that there are large amounts of non-coding junk DNA which is under no selection pressure
For people who may not understand how we know this -- there are "conserved" sections of DNA which don't change much over time. Very similar in mice and humans for example, because it performs important regulatory work, and if it doesn't, the animal dies.
There are other large sections where it can disappear and nothing of consequence seems to happen. And we know that, because some people have micro-deletions or other variants in the region and they are completely benign.
We will eventually identify a better classification than "intron" and "exon" to sort through the "junk" from "critical junk" but we are really only starting to untangle the situation.
It's benign in the tested environment. You can't really test every possible environment (diet, climate, etc), so it seems roughly comparable to the halting problem; Does there exist a micro-deletion that in some environment causes this life to halt? It's unsolvable at DNA scale.
"Benign" in a clinical genetics context means "the variant is not linked to observed phenotype in patients". Patient lives their life without disability, reproduces without issue.
Not really productive to imagine scenarios to unlock some hidden use. Sometimes junk is junk. Evolution is not hyper-efficient in the short term, stuff happens.
Yeah I feel pretty incredulous about this too. Surely you would want to see a few hundred generations reproducing with the change before you could begin to say with any confidence that it might not have an effect.
>> non-coding junk DNA which is under no selection pressure
> "conserved" sections of DNA which don't change much over time
I'm not a biologist. I imagine DNA that does nothing and is under no selection pressure should have a bunch of random mutation accumulated - the opposite of what you described.
> There are other large sections where it can disappear and nothing of consequence seems to happen.
So then we don't know for sure? I thought surely we must have some more rigorous means of identifying junk for OP's comment to be true, but trial and error removal seems really weak.
For people who may not understand how we know this -- there are "conserved" sections of DNA which don't change much over time. Very similar in mice and humans for example, because it performs important regulatory work, and if it doesn't, the animal dies.
There are other large sections where it can disappear and nothing of consequence seems to happen. And we know that, because some people have micro-deletions or other variants in the region and they are completely benign.
We will eventually identify a better classification than "intron" and "exon" to sort through the "junk" from "critical junk" but we are really only starting to untangle the situation.