How does gene therapy differ from directly replacing a mutated gene sequence?

The distinction between traditional gene therapy and direct gene editing lies in their precision and mechanism of action.

Gene Therapy
Gene therapy typically involves the introduction of a normal, functional gene into an individual's genome to compensate for a disease-causing mutation. When this normal gene is inserted into a cell's nucleus, it often integrates into a random chromosomal site rather than the specific location of the defective allele. While this can restore the production of a necessary protein, it carries the risk of causing new mutations if the gene integrates into another functional gene.123

Gene Editing
In contrast, gene editing technologies, such as CRISPR-Cas9, allow for highly specific modifications to the DNA sequence. Rather than simply adding a new gene, researchers can target a precise nucleotide sequence to remove, replace, or repair the existing mutated segment. This approach offers greater control over the genetic change, directly addressing the underlying error at its original site.3

While gene therapy has been used in clinical trials, it remains distinct from the precise, targeted "cut-and-paste" capabilities provided by modern gene-editing tools.13