Use in clinical context
The principle behind gene therapy is that protein production can be altered. This can be in cells that do not produce a particular protein when they should, or they produce an altered version of the protein that does not function correctly.
Gene therapy delivers a functioning copy of a gene to cells. This is usually done using a non-infectious virus to deliver the gene to the target cells. It does not integrate the new DNA into the chromosomes, but exists as free-floating DNA in the nucleus where it can be transcribed into mRNA. Once transcribed, the mRNA is processed in the same way as mRNA transcribed from chromosomal DNA.
Gene therapy is currently most practical where a disease affects a single organ, as delivery of the gene can be targeted to that organ. Currently gene therapy in the UK is only approved by NICE for an inherited eye disorder. Eyes are particularly amenable to gene therapy, as it is relatively easy to deliver the therapy to the cells that require the gene.