1. Gene Therapy Learning Goal: To explore gene therapy. Success Criteria:
I know I am succeeding when I can…
explain that gene therapy attempts to correct the effects of a defective gene by inserting a normal gene in its place
describe the process of gene therapy
explain the drawbacks to gene therapy
discuss the areas in which gene therapy has been most successful

2. Gene Therapy
gene therapy: the process by which defective genes in a genome are corrected with a normal copy of the gene
the cells in which the gene needs to be replaced or repaired are known as target cells
in order to insert a normal gene into the target cells, a specialized DNA sequence, called a vector (plasmid or virus) is used

3. Gene Therapy
viral DNA is removed or altered so that the viruses cannot harm the cells they enter
copies of the DNA that include the normal human gene are placed inside virus and are incorporated into the virus’s own DNA
large numbers of these viruses are used to infect the target cells in an attempt to insert the normal human DNA into the cells’ genome

4. Types of Gene Therapy
Somatic Gene Therapy: adds the desired gene to cells that are NOT reproductive cells (only that individual will be impacted)
Germline Gene Therapy: permanently adds the desired gene to reproductive cells that produce egg or sperm cells (effects will be passed on offspring and future generations)

5. Limitations of Gene Therapy
the normal gene inserted into the target cell must work for the duration of the target cell’s life
it is not possible to control where a gene is inserted and it may disrupt the function of that gene resulting in more health challenges
immune system may attack the foreign virus
Still in experimental stages

6. Issues of Gene Therapy Cont’d…
the virus may recover its ability to cause disease once it is in the target cell
many disorders are caused by more than one gene and it is difficult to fix all the genes
once the gene is transferred into the target cell, it needs to be regulated so that it is expressed at the required times
the vector that is chosen must be able to reach all or most of the target cells specifically
Still in experimental stages
Once the gene is transferred into the target cell, it needs to be regulated so that it is
expressed at the required times. For example, a gene that regulates the production of
insulin would need to be able to detect a low sugar level in the blood. If sugar levels
are low, the gene that directs the production of insulin should not be turned on.

7. Successes of Somatic Gene Therapy
gene therapy has been used to treat a form of childhood blindness (LCA) is caused by a genetic defect in pigment layer cells on the retina
1. An eye syringe is used to inject viruses carrying a normal gene behind the
patient’s pigment cell layer.
2. The viruses infect the pigment cells and deliver the normal gene.
3. The cells incorporate the normal gene, which restores normal functioning.
This results in improved vision.

8. Successes of Somatic Gene Therapy
may be able to use gene therapy to cure Duchenne muscular dystrophy (DMD)
people who suffer from DMD experience rapid muscle degeneration and have about 1/3 to 1/2 the usual life expectancy
it is x-linked so mostly affects males
scientists have successfully repaired the incorrect base-pair sequence in the faulty Dystrophin gene in mice
All the work thus far has been in mice, but it is possible that human
trials will begin in two or three years.

9. Successes of Somatic Gene Therapy
sounds move tiny hairs in the cochlea of the inner ear
the hairs translate sound vibrations into nerve signals that are delivered to the brain
normally, when hairs are damaged and hearing is lost, the change is permanent
1. An eye syringe is used to inject viruses carrying a normal gene behind the
patient’s pigment cell layer.
2. The viruses infect the pigment cells and deliver the normal gene.
3. The cells incorporate the normal gene, which restores normal functioning.
This results in improved vision.

10. Successes of Somatic Gene Therapy
in 2005, a virus was used to deliver a gene that stimulated the growth of new hairs in the cochlea in deaf guinea pigs
up to 80 % of the guinea pigs’ ability to hear was restored(!)
1. An eye syringe is used to inject viruses carrying a normal gene behind the
patient’s pigment cell layer.
2. The viruses infect the pigment cells and deliver the normal gene.
3. The cells incorporate the normal gene, which restores normal functioning.
This results in improved vision.

11. Homework read pages 249-251 in your text answer 6.5 questions #1-5
Centrioles are involved in the formation and organization of spindle fibres, which attach to the chromosomes during cell division. The centromere helps anchor the chromosomes to the spindle fibres