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  1. I think it’s important to remember that the application of CRISPR is more limited in scope than it may intially appear. As far as I know (maybe there have been further developments I’m unaware of) CRISPR can be used as a therapeutic in two ways: either as a way to induce a break in DNA at a specific location, leaving it vulnerable to error-prone repair mechanisms, or as a way to swap certain DNA bases to other i.e. A to T, C to G and vice versa. This is interesting if you’re trying to disable a problematic gene (the former case) or swap a base at a key position that induces a disease state (the latter case), but the fact is that many genetic diseases are too complex to approach in this manner.

    [This](https://static.wixstatic.com/media/b8a9a2_a1aacc180f344929938b06ea61676efd~mv2.jpg/v1/fill/w_555,h_357,al_c,q_80,usm_0.66_1.00_0.01/b8a9a2_a1aacc180f344929938b06ea61676efd~mv2.jpg) figure illustrates the relationship between allele frequency and effect size. For anyone not familiar with these terms, allele frequency refers to how common the DNA bases that induce a disease are, and effect size is how “bad” the disease is. I feel like excitement around CRISPR is generally focused around the idea of curing a disease by fixing the mutation responsible. In reality, the number of diseases caused by a few very specific mutations we could conceivably edit with CRISPR are actually pretty rare. In the figure I linked these are low frequency, high effect diseases. One problem with the idea of genome editing as a therapeutic is that a huge number of genetic diseases are the result of a confluence of many more common mutations that individually are almost impossible to measure in effect, but collectively cause major problems. The latter can’t really be cured with gene editing, and correct me if I’m wrong but I believe those types of diseases tend to be more common than the “one and done” type diseases.

    CRISPR tends to be extremely hyped up, especially on sites like reddit. It is cool and it’s a particularly useful tool in the lab, but the idea commonly peddled by less scientific literate media that we are going to be printing custom humans with it in a matter of years represents a gross misunderstanding of what CRISPR actually is and how it can be used. CRISPR is ultimately just another tool in the toolbox, and the cool thing about biomedical science is we’re always discovering new tools or better ways to use the old ones. I don’t know why writing this is what I’m doing as a break from my thesis

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