C9orf72 is a gene with repeat length variation. A GGGGCC seq…

C9orf72 is a gene with repeat length variation. A GGGGCC sequence is repeated in this gene. In most people, this sequence is repeated less than 20 times. However, in some people with amyotrophic lateral sclerosis (ALS) this sequences is repeated hundreds of times. The expanded repeat in the C9orf72 gene leads to the production of a toxic protein. Scientists are currently trying to develop a gene therapy to treat ALS caused by the expanded repeat in C9orf72. What should be delivered to cells to treat ALS caused by an expanded repeat in the C9orf72 gene? Chose the best answer: