In most gene therapy studies, a "normal" gene is inserted into the
genome to replace an "abnormal," disease-causing gene. A carrier
molecule called a vector must be used to deliver the therapeutic
gene to the patient's target cells. Currently, the most common
vector is a virus that has been genetically altered to carry normal
human DNA. Viruses have evolved a way of encapsulating and
delivering their genes to human cells in a pathogenic manner.
Scientists have tried to take advantage of this capability and
manipulate the virus genome to remove disease-causing genes and
insert therapeutic genes.Target cells
such as the patient's liver or lung cells are infected with the
vector. The vector then unloads its genetic material containing the
therapeutic human gene into the target cell. The generation of a
functional protein product from the therapeutic gene restores the
target cell to a normal state.
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