Precisely deleting exactly three letters at a time from the repeat sequence in the Huntington gene is necessary to avoid shifting the gene's reading frame.

“the challenges are the repeats happen within the coding region of the gene so the region that is important for making the protein sequence so in order to uh make the resulting edit um successful you have to do it very precisely you cannot delete um you have to delete exactly um know three letters at a time from from the repeat sequence otherwise you would shift the frame and the gene”