Why are there so many side effects to modifying Dna sequences? Why would it not be considered safe to altern Humans’ Dna and what makes it dangerous?
In: Biology
No expert here, but I believe it’s because of our limited understanding of how DNA works. From what I’ve seen, we seem to understand what some of the pieces do, but not others. Also, there seems to be an incomplete understanding of how altering one little piece affects the organism as a whole.
Maybe someone more knowledgeable in this field could explain it better.
If I take a technique like crispr cas9, while not being a genetic expert, 3 problems come to mind.
Crispr cas9 is a technique used by scientist those past few years for gene editing, it was described as “promising” in terms of genome editing for humans in order to fight genetic diseases. The point is simple : You cut out “bad DNA” and replace it with “good DNA” and tada, your debilitating fatal genetic mutation doesn’t exist.
1 : It woks at the right target at like 1% which is honestly not that bad but if your point is to completely remove a defective gene, then it won’t work totally.
2 : It’s not selective at 100%. Sometimes it cut the wrong genes at the wrong place. Which can be dramatic depending on where it cuts.
3 : Sometimes it cuts where it needs to be, but then doesn’t put the good DNA. You’re not left with a “hole” in your DnA, they will repair it in whatever way they can, but it can do something called “non homologous end joining” : they fix the “hole” in the DNA by raccording the two extremities of the hole : Basically the bad gene is gone but there is no good gene to replace it.
Depending on the genetic diseases, it can do nothing (when the bad gene is basically a defective gene, so no gene is pretty much the same) but it can also cause a new problem. Like when the bad gene is a functionning gene but TOO functionning. No gene =/= bad gene, and if this gene is necessary for a cell survival, then it can lead to serious damages in someone body.
Off target effects. Gene editing is easy so long as you don’t fret over the viability of the subject, which tends to be an issue with humans.
At the moment, when we genetically modify something we do it lots of times and pick the ones with the results we were looking for (and without results we really don’t want).
We’re also not 100% sure every gene only does one thing (in fact we know some of them do lots of things).
So if you’re working with plants or microbes, you can do this and just discard the “bad” ones, but obviously we don’t want to do that with humans.
Because there’s literally billions of genes to deal with, and nobody really knows how they interact with one another. Maybe you modify gene #4567 to have blond hair, but that gene also interacts with gene #87624 which is responsible for how much calcium there’s in your bones. So you get a blond human, but with glass bones. There are so many places where you could fuck up that it’s not worth the risk.
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