1. 6.5 Gene Therapy Pages 249-251

2. Gene therapy Defective genes are corrected using a normal copy of the gene.

3. How gene therapy works: Replacing a mutated gene that causes disease with a healthy copy of the gene. Inactivating, or “knocking out,” a mutated gene that is functioning improperly. Introducing a new gene into the body to help fight a disease.

4. Target cell One of the cells that contain the faulty gene to be corrected.

5. Vector Any agent, such as a plasmid or a virus, capable of inserting a piece of foreign DNA into a cell.

6. Limitations Viruses vectors are a good choice for mammals, but plasmid vectors are not. A cold virus is a good choice to target lung cells but not bone cells.

7. Process Step 1: Remove or alter viral DNA Step 2: Human DNA coding for the normal gene are inserted into virus and incorporated into the viral DNA. Step 3: Large numbers of virus infect human cells.

8. Tragedies A teenager died in 1999 when he had an unexpected severe immune response to the virus serving as the vector. Leukemia has developed in two children who were treated with gene therapy.

9. The hurdles: Multiple treatments are required. No control over where gene is inserted. The body may attack the virus. The virus may attack the cell. Many disorders have multiple genes at play. Regulation of genes such as insulin Ability of vector to reach target cells

10. Successes Restoring vision Restoring hearing Repairing gene causing Duchenne Muscular Dystrophy.

11. Inherited Blindness Added photoreceptors to dogs to correct vision Children regain sight after pigment layer cells are repaired.

12. Duchenne Muscular Dystrophy

13. Deafness Up to 80% of Guinea pigs’ hearing was restored when genes were added to promote the growth of hairs in the cochlea.