Human Gene Therapy :: Biology Genetics Essays

Human Gene Therapy Everybody carries about half a dozen defective genes. Many don't know this, unless someone they know is affected by a genetic disorder.(1) The genetics of many diseases are passed from one generation to the next by inheriting a single gene, such as Huntington's disease. Many other diseases and traits are influenced by a collection of genes.(4) About one in ten people has, or will develop, an inherited genetic disorder. Approximately 2,800 specific conditions are known to be caused by defects, or mutations, in just one gene. Most of us don't suffer any harmful effects from our defective genes because we carry two copies of nearly all genes. In most cases one normal gene is enough to avoid all the symptoms of disease. If the affected gene is recessive, and we inherit two copies of the gene, the disease will develop. If the affected gene is dominant, only one copy is enough produce the disease. There are also X-chromsome linked genetic diseases.(1) A potential approach to the treatment of genetic disorders in humans is gene therapy. Gene therapy is the delivery of a correct version of a mutated gene to a cell, where its expression will produce the normal protein and restore normal cellular function. The mutated gene must be delivered to the nucleus of the cell.(2) There are essentially two forms of gene therapy, somatic gene therapy and germline gene therapy. Somatic gene therapy involves the manipulation of gene expression in cells that will be corrective to the patient but not inherited by the next generation.(4) Germline gene therapy involves the replacement of defective genes in the germline cells, which contribute to the genetic heritage of the offspring. It has the potential to affect not only the individual being treated, but also his or her children. Germline therapy would change the genetic pool of the entire human species, and future generations would have to live with that change. It is not likely germline therapy will be tried on humans in the near future due to ethical problems and technical difficulties.(1) In vivo gene transfer is the introduction of genes to cells at the site at which they are found in the body. Ex vivo gene transfer is the transfer of genes into viable cells that have been temporarily removed from the patient and are then returned following treatment.(6) Foreign DNA can be injected into the cell, or its entry can be facilitated by various chemical or electronic ways, but these methods aren't very efficient.