How can gene therapy repair or compensate for a disease-causing mutation?

Gene therapy aims to treat genetic diseases by introducing a normal gene into an individual's genome to repair or compensate for a disease-causing mutation. This process generally follows two primary strategies:12

• Functional Compensation: Early approaches focused on providing a functional copy of the mutated gene, which is either inserted into the genome or maintained as an extrachromosomal unit. This allows the cell to produce the necessary protein, potentially restoring the individual to an undiseased phenotype.23
• Direct Correction: More advanced techniques, such as gene editing using CRISPR-Cas9, allow researchers to target specific nucleotide sequences. By creating a precise break in the DNA, the cell can be directed to replace the mutated "bad" sequence with a "good" sequence.13

To deliver these genes into target cells, scientists often use viral vectors, which are modified viruses that efficiently enter cells and transport the therapeutic genetic material. While these methods offer significant potential to alleviate human suffering, they raise complex ethical and safety concerns, including the risk of unintended mutations or immune responses.423