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Gene Therapy
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AP Biology
Unit 2
What is Gene Therapy?
• A way to treat or cure diseases by inserting
the “correct” DNA into the cell.
• Most promising for diseases caused by a
single gene defect (ex. hemophilia)
• Still in the experimental stages
• Clinical trials have been done on humans
The Big Picture
Image taken without permission from http://www.fda.gov/fdac/features/2000/gene.html
Ex vivo
• Means it occurs outside of the body
• Steps:
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Defective cells are taken out of the patient
Add functional gene into defective cells
Return these cells to the patient’s body
Has been used to treat hemophilia, and
adenosine deaminase deficiencies (leads to
immune system problems)
In vivo
• Means it occurs in the patient’s body
• Insert the genes directly into the patient’s
cells
• Ex. using an aerosol spray containing
functional genes that are are mutated in
cancer cells to treat lung cancer.
• Still in the early stages of experimentation
Challenges
• Find appropriate vectors
– currently recombinant viruses and plasmids are being
tested
• Make sure vectors can be taken up by human cells
properly
• Ensure that new gene is inserted into human
genome properly and proteins are expressed
correctly
– Could be very problematic if it inserts itself in the
wrong place and disrupts transcription of a crucial
protein
More challenges
• How to make sure the functional gene gets
to all the cells that need it
• How to sustain the cells that got the
functional gene– cells die after a while!
• How to control how the immune system
responds to the vector