ROLE OF GENE THERAPY IN SURGERY

Abstract

The complete genetic makeup of an individual is referred to their genome. Thus, in human cells the genome is composed of 23 pairs of chromosomes within the nucleus, each chromosomes containing a single, linear, double helical strands of DNA. The humane genome contains approximately 3 billions base pairs, and is thought to contain about 30 thousands different genes, most of which encode polypeptides. A small minority of genes encode RNA molecules. Gene is thought to be a segment of DNA molecule possessing a code for amino acid sequence of a polypeptide chain. This model however appears to be inadequate to elucidate precise mechanism of gene operation. There are about 50 to 100 thousand DNA sequences which code for RNA or protein products in man. These are called structural genes. On analysis of a structural gene, which reveals coding sequence called "exons" which are interrupted by non coding sequences called "introns". "Introns" are initially transcribed but are not represented in mature (mRNA) or in the final protein product. The gene also possesses extensive "flanking regions". They are important in regulation and the "start" and "stop" signals. Molecular "treatment” requires, the molecular manipulation or alteration of a designated ”target” population of cells. Essentially, this change can be effected in one of two ways: by ex-vivo modification, with the material being re-introduced into the body after modification, or by in-vivo modification, done in situ. Whatever approach is adopted, the treatment will probably involve one of the following: gene replacement, gene addition, and gene control. Gene and their products can be delivered to a target tissue using either an ex-vivo or an in-vivo approach. Both approaches carry several advantages and drawbacks. Ex-vivo techniques rely on the isolation and cultivation of selected cells, their transfection in vitro and subsequent transplantation to a host, usually in an autologous manner. It is more laborious and expensive than in vivo gene transfer techniques in which genes are introduced directly to the target tissue bypassing the need for cell culture. In vivo methodologies can utilize some of the same vectors and transfection systems commonly used ex-vivo. New genes can be introduced into cells using either virus common viral vectors for gene therapy include: retroviral vectors, adenoviral vectors, adeno-associated viral vectors and herpes simplex viral (HSV) vectors.