Gene therapy is designed to introduce genetic material into cells to compensate for abnormal genes or to make a beneficial protein. If a mutated gene causes a necessary protein to be faulty or missing, gene therapy may be able to introduce a normal copy of the gene to restore the function of the protein.
A gene that is inserted directly into a cell usually does not function. Instead, a carrier called a vector is genetically engineered to deliver the gene. Certain viruses are often used as vectors because they can deliver the new hi gene by infecting the cell. The viruses are modified so they can't cause disease when used in people. Some types of virus, such as retroviruses, integrate their genetic material (including the new gene) into a chromosome in the human cell. Other viruses, such as adenoviruses, introduce their DNA into the nucleus of the cell, but the DNA is not integrated into a chromosome.
The vector can be injected or given intravenously (by IV) directly into a specific tissue in the body, where it is taken up by individual cells. Alternately, a sample of the patient's cells can be removed and exposed to the vector in a laboratory setting. The cells containing the vector are then returned to the patient. If the treatment is successful, the new gene delivered by the vector will make a functioning protein.
Human gene therapy
Genetic disorders affect about one in every ten people. Some, like cystic fibrosis, can have consequences early in a child's life while others, like Huntington's disease don't show up until later in life.
Preventing genetic disorders can be difficult. Unlike regular diseases whichare a result of external factors, genetic diseases are caused by our very own DNA. When the genetic code in a gene is altered, the gene can become defective.
Genetic disorders are hereditary. When the defective gene is passed onto an offspring, there is a risk that that offspring will develop that genetic disorder. Some genetic disorders are caused by dominant genes, requiring only a single gene for the disease to develop. Others are caused by recessive genes which require two copies of the defective gene, one from each parent, to cause the disease.
There is, however, a new revolutionary new technique called gene therapy aimed at treating and curing genetic disorders using cloned genes. It involves replacing defective genes with copies of the correct genes. Somatic gene therapy is used to treat people with existing genetic disorders. Germline gene therapy is used to insert corrected genes into the reproductive cells so that future offspring will not contain the defective genes of the parent.