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Gene Therapy. Kortlynn Johnson. What is Gene Therapy?. A technique for correcting defective genes responsible for disease development 1. Correcting Faulty G enes. Doctors may use 1 of these approaches 1 :.

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gene therapy

Gene Therapy

Kortlynn Johnson

what is gene therapy
What is Gene Therapy?
  • A technique for correcting defective genes responsible for disease development1
correcting faulty g enes
Correcting Faulty Genes

Doctors may use 1 of these approaches1:

  • A normal gene may be inserted into a nonspecific location within the genome to replace a nonfunctional gene.
    • *Most common*
  • An abnormal gene could be swapped for a normal gene through homologous recombination.
  • The abnormal gene could be repaired through selective reverse mutation, which returns the gene to its normal function.
  • The regulation (the degree to which a gene is turned on or off) of a particular gene could be altered.
how does gene therapy work 1
How Does Gene Therapy Work?1
  • In most gene therapy studies, a "normal" gene is inserted into the genome to replace an "abnormal," disease-causing gene.
    • Carrier molecule  Vector
    • Most common carrier  Virus
types of vectors 1
Types of Vectors1
  • Retroviruses
    • Create double-stranded DNA copies of their RNA genomes
    • These copies of its genome can be integrated into the chromosomes of host cells
  • Adenoviruses
    • Have double-stranded DNA genomes that cause respiratory, intestinal, and eye infections in humans.
types of vectors 11
Types of Vectors1
  • Adeno-associated viruses
    • Small, single-stranded DNA viruses that can insert their genetic material at a specific site on chromosome 19
  • Herpes simplex viruses
    • Double-stranded DNA viruses that infect a particular cell type – neurons
non viral approaches 1
Non-Viral Approaches1
  • Direct introduction of therapeutic DNA into target cells
    • Simplest method
    • This approach is limited in its application because it can be used only with certain tissues and requires large amounts of DNA.
non viral approaches 11
Non-Viral Approaches1
  • Another nonviral approach involves the creation of an artificial lipid sphere with an aqueous core.
    • This liposome, which carries the therapeutic DNA, is capable of passing the DNA through the target cell's membrane.
applications of gene therapy 1
Applications of Gene Therapy1
  • Current
    • Researchers also are experimenting with introducing a 47th (artificial human) chromosome into target cells.
    • This chromosome would exist autonomously alongside the standard 46 --not affecting their workings or causing any mutations.
applications of gene therapy 11
Applications of Gene Therapy1
  • It would be a large vector capable of carrying substantial amounts of genetic code, and scientists anticipate that, because of its construction and autonomy, the body's immune systems would not attack it.

**A problem with this potential method is the difficulty in delivering such a large molecule to the nucleus of a target cell.**

gene therapy going global 1
Gene Therapy: Going Global1
  • The School of Pharmacy in London is testing a treatment in mice, which delivers genes wrapped in nanoparticles to cancer cells to target and destroy hard-to-reach cancer cells. (March 2009)
  • UK researchers from the UCL Institute of Ophthalmology and Moorfields Eye Hospital NIHR Biomedical Research Centre announced results from the world’s first clinical trial to test a revolutionary gene therapy treatment for a type of inherited blindness. The results show that the experimental treatment is safe and can improve sight. (April 2008)
gene therapy going global 11
Gene Therapy: Going Global1
  • In France, gene therapy performed on children suffering from Severe Combined Immunodeficiency was halted because one of the patients developed leukemia as a direct consequence of the treatment. (October 2002)4
gene therapy going global 12
Gene Therapy: Going Global1
  • China’s first gene therapy was just recently approved in 2003.
  • China's medicines authority approved the cancer therapy after it achieved promising results in a clinical trial.
setbacks for advancement 1
Setbacks for Advancement…1
  • The Food and Drug Administration (FDA) has not yet approved any human gene therapy product for sale.
setbacks for advancement 11
Setbacks for Advancement…1
  • In 1999, gene therapy suffered a major setback with the death of 18-year-old Jesse Gelsinger. Jesse was participating in a gene therapy trial for ornithine transcarboxylase deficiency (OTCD).
  • He died from multiple organ failures 4 days after starting the treatment. His death is believed to have been triggered by a severe immune response to the adenovirus carrier.
some ethical questions to consider about gene therapy 1
Some Ethical Questions to Consider about Gene Therapy1
  • What is normal and what is a disability or disorder, and who decides?
  • Are disabilities diseases? Do they need to be cured or prevented?
  • Does searching for a cure demean the lives of individuals presently affected by disabilities?
  • Preliminary attempts at gene therapy are exorbitantly expensive. Who will have access to these therapies? Who will pay for their use?
pros and cons of gene therapy 5
Pros and Cons of Gene Therapy5



  • Wipe out genetic disease before it can begin and eliminate suffering for future applications
  • Good technique for diseases not researched yet
    • People carry defected genes and may be unaware
    • Gene therapy can eliminate the consequences of carrying these genes
  • Putting human fate into our own hands
    • Creating a “superior race”
    • “Playing God”