The challenge in gene therapy is how to get the correct genetic material to the appropriate cells. According to Encyclopedia Britannica online 1998 there are three types of delivery systems- a viral vector, a chemical method or a physical method. The most common and accurate is a viral vector. Technology has developed vectors, which encapsulate therapeutic genes, in order for delivery to defected cells. Many vectors are actually viruses.
Viruses are efficient in targeting cells and delivering information.
According to PBS online 1998, viruses are actually genes wrapped in a protein coat. This protein coat is unique since it has special proteins that bind to the surfaces of cells. Once bonded they either force their way in or are sucked into the cell itself. The virus can either be mixed with cells taken out of the body or they can be injected directly into the body. One type of virus actually inserts its genetic code directly into the chromosome of the host cell.