oh man what are the effects of mercury poisoning in the genes??? i thought they only poisoned the brain.

Ok, so. You know how big the human genome is (we have about 20k to 25k protein-coding genes, but keep in mind that a good part of our genome is made out of genes that don’t code protein at all! our DNA is really Big). So, you can imagine how important it is to replicate and translate these thousands of nucleotides correctly, since any tiny mistake can either be fatal or lead to serious illnesses.
That’s why our DNA has a myriad of repair mechanisms for when shit goes wrong! There are a series of mechanisms we studied in class, such as repair by excision or by recombination, but the one that interests us in this explanation is the so-called “error prone DNA repair mechanism” (you can imagine how much potencial of Fucking Shit Up this one has)
Error prone DNA repair is triggered by an SOS response. In cases of radioactive or heavy metal contamination, your chromossomes might be severely affected by those substances. Like, in some cases an entire “arm” of the chromossome can fall off! (this sort of mutation is called chromossomal mutation btw) Imagine how serious that is. In short, the SOS response is basically your repair mechanisms freaking the fuck out and trying to put that arm back at any cost because thousands of nucleotides are in that arm, and you can’t afford to lose any bit of DNA. So, most of the time the arm can come back, but in haphazard fashion, so the genes are all in the wrong order and stuff.
Now, imagine a severe heavy metal contamination case, such as the one that happened in Minamata, Japan, a few decades ago (it was mercury in that case), or the one happening in Flint, Michigan, right now (it’s lead contamination, mostly). You’ve got a LOT of cells going through those mutations, all over the body, and your repair mechanisms can’t fix all those damages. Thus, there’s all those neurological complications that are basically incurable and all
I’d put some pictures to clarify my explanation but i’m on mobile tumblr and had this class literally yesterday, so i didn’t have time to study this subject more deeply. There’s probably some gross errors or oversimplifications, but it’s just so you realize how fucked up shit really is. It’s absolutely amazing that our repair mechanisms normally work so efficiently, which is the reason why you dont instantly get cancer every time you expose your skin in the sun or take an X-ray. These tiny hardworking molecules are nothing short of miraculous and it fucks me up every damn time