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Gene Therapy
What is Gene Therapy?
• Defective genes make non-functional
proteins, creating genetic disorders
• Gene therapy corrects defective genes by
inserting a functional gene somewhere
into the affected chromosome
• Gene therapy can also repair bad RNA
How Gene Therapy Works
• Viruses are genetically altered to carry
therapeutic human genes
• Virus is a “vector” for the good genes
• Virus infects target cell by injecting its
DNA or RNA into cell’s genome
• Therapeutic genes are incorporated into
target cell’s genome, and correct proteins
are made
How Gene Therapy Works
Uses for Gene Therapy
• Ex: Severe Combined Immune Deficiency
(Bubble Boy) Syndrome
- patients don’t make enzyme needed for
immune system development
- send therapeutic genes to bone marrow
cells (make immune system cells)
- bone marrow now can make immune
cells, and boy no longer lives in bubble 
David Vetter, Bubble Boy
Uses for Gene Therapy
• Huntington’s Disease: send in RNA that
interferes with and destroys faulty RNA
• Hemophilia, Cystic Fibrosis, Thalassemia:
substitute faulty mRNA with good mRNA
• Instead of fixing adults, we could do gene
therapy on sperm, eggs, and embryos
(designer babies!)
Problems with Gene Therapy
• Short term fix (must get continued viral
injections)
• Immune system can respond to viral
vector, killing patient
• Only fixes disorders caused by one genewhat about multi-gene disorders?
Current Status
• FDA has not approved use of gene
therapy in U.S.
• Based on trial done in France that killed
two boys, including David Vetter (bubble
boy), in 1999 and 2003.
• Is the risk worth the lives that could be
saved?