Gene TherapyGene Therapy

AP BiologyUnit 2

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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:– 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