[irjustin]

I wondered the same thing and according to Gemini a chromosome is massive vs a few genes. Cutting it out with crispr is possible, but it's too big of a change and would lead to cell death rendering whatever change either useless or kills the host given the possible stage this treatment could be delivered at.

[samus]

Since the presence of that chromosome causes problems in an organism that functions normally with just two of these chromosomes, the change is actually not that big. And the therapy might also not be intended for adults or even children - most of the developmental impediments have already happened at that stage, and neither cutting out the extra chromosome or silencing it will fix this up.

[ceejayoz]

Now ask Gemini what chromosomal anomaly causes Downs. It will likely be enlightening.