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Almost always, building something is harder than tearing it down. Similarly, knocking in genes poses a greater challenge than knocking them out. It’s a reality that researchers will have to overcome in order to get the most out of gene editing. Knocking in genes allows scientists to study the effects of specific gene variants, to use reporter genes like green fluorescent protein to track gene products in time and space, to probe genome regulation, and ultimately, to repair disease-causing genes. “It’s a really effective way to interrogate every base of a gene,” says Greg Findlay, an MD/PhD candidate at the University of Washington.
CRISPR-Cas9, a gene editing technology known for its user-friendliness, can knock genes in or out. Knocking out a gene involves inserting CRISPR-Cas9 into a cell using a guide RNA that targets the tool to the gene of interest. There, Cas9 ...