Final answer:
Gene therapy is the treatment method that corrects genetic diseases by introducing non-mutated genes to replace defective genes, often using viral vectors.
Step-by-step explanation:
The treatment of genetic diseases by the administration of genes to correct an absent or defective gene is known as gene therapy. This technique involves the introduction of a non-mutated, functional gene to replace a defective gene. By doing so, it can cure diseases caused by genetic mutations, like cystic fibrosis and sickle cell anemia. The new gene can be introduced into the patient's cells using a viral vector, such as an adenovirus. While still considered experimental, gene therapy holds great promise for curing heritable diseases and has had some successful applications in diseases like severe combined immunodeficiency (SCID).