Tuesday, 23 April 2013

Pedro, Dani and Alex project.


Gene therapy is the use of DNA as a pharmaceutical agent to treat disease. It derives its name from the idea that DNA can be used to supplement or alter genes within an individual's cells as a therapy to treat disease. The most common form of gene therapy involves using DNA that encodes a functional, therapeutic gene to replace a mutated gene. Other forms involve directly correcting a mutation, or using DNA that encodes a therapeutic protein drug (rather than a natural human gene) to provide treatment. In gene therapy, DNA that encodes a therapeutic protein is packaged within a "vector", which is used to get the DNA inside cells within the body. Once inside, the DNA becomes expressed by the cell machinery, resulting in the production of therapeutic protein, which in turn treats the patient's disease.
Gene therapy was first conceptualized in 1972, with the authors urging caution before commencing gene therapy studies in humans. The first FDA-approved gene therapy experiment in the United States occurred in 1990, when Ashanti DeSilva was treated for ADA-SCID. Since then, over 1,700 clinical trials have been conducted using a number of techniques for gene therapy.


Gene therapy may be classified into the two following types:


In somatic gene therapy, the therapeutic genes are transferred into the somatic cells, or body, of a patient. Any modifications and effects will be restricted to the individual patient only, and will not be inherited by the patient's offspring or later generations. Somatic gene therapy represents the mainstream line of current basic and clinical research, where the therapeutic DNA transgene (either integrated in the genome or as an external episome or plasmid) is used to treat a disease in an individual.


In germ line gene therapy, germ cells, i.e., sperm or eggs, are modified by the introduction of functional genes, which are integrated into their genomes. This would allow the therapy to be heritable and passed on to later generations. Although this should, in theory, be highly effective in counteracting genetic disorders and hereditary diseases, many jurisdictions prohibit this for application in human beings, at least for the present, for a variety of technical and ethical reasons.



Preventive gene therapy is the repair of a gene with a mutation associated with a progressive disease, prior to the expression of a medical condition, to prevent that expression.One case study of preventive gene therapy: Retinitis PigmentosaBlindness can be caused by multiple genetic diseases. Many gene therapy efforts have been focused on treating blindness as a result of moderate success in preventing the loss of vision in multiple animal models. To do this, blindless must be diagnosed early on before the symptoms begin. The retina, which is located in the back of the eyeball, is the first step in processing visual information, accordingly it is a common target in exploration of the genetic issue that leads to blindness. One autosomal genetic disease that has been extensively researched is retinitis pigmentosa (RP) because it has excellent animal models for genetic therapy techniques to treat blindness.Within a single disease, there can be multiple preventative gene therapy strategies used to combat the progression of the symptoms. Most people who suffer from RP are born with rod cells that are either dead or dysfunctional, so they are effectively blind at night time, since these are the cells responsible for vision in low levels of light. What follows often is the death of cone cells, responsible for color vision and acuity, at light levels present during the day. Loss of cones leads to full blindness as early as five years old, but may not onset until many years later. There have been multiple hypotheses about how the lack of rod cells can lead to the death of cone cells. Pinpointing a mechanism for RP is difficult because there are more than 39 genetic loci and genes correlated with this disease. In an effort to find the cause of RP, there have been different gene therapy techniques applied to address each of the hypotheses.


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