Which statement best captures the essence of gene therapy?

Gene therapy is a medical technique that focuses on addressing genetic disorders by correcting or modifying the underlying genetic defects that cause diseases. This approach aims to directly alter the genetic material—DNA or RNA—within a patient's cells to restore normal function or to introduce new functions that can alleviate or cure the disease. By targeting the specific genetic basis of a condition, gene therapy has the potential to provide long-lasting solutions to diseases that were previously considered untreatable, particularly genetic disorders, certain types of cancer, and viral infections.

The other options do not accurately represent the fundamental principles of gene therapy. Altering an organism's diet, while beneficial for overall health, does not involve genetic manipulation and is more related to nutritional science. Cosmetic changes to genetic traits focus on superficial enhancements rather than addressing health issues at the genetic level. Lastly, integrating various genes from unrelated species pertains more to genetic engineering or transgenics rather than the therapeutic intent of gene therapy, which specifically seeks to repair or modify defective genes to treat diseases.