What is Gene Therapy
Gene therapy is the therapeutic delivery of nucleic acid polymers into a patient’s cells as a drug to treat disease.
Technology of Gene Therapy
The objective of gene therapy is to rescue mutant phenotypes by providing deficient cells with a normally functioning copy of the gene associated with the disease. In such rescues the mutant cells are complemented by the rescuing gene and reverted to wildtype function. This paradigm for gene therapy is only be useful in treating diseases caused by recessive mutations such as cystic fibrosis in which in a single functional copy of the gene is sufficient for the viability of the individual(Hawley, Lieu, Fong& Hawley, 1994). Diseases caused by dominant alleles such as Huntington’s disease would most likely not be cured under this scheme because the presence of the mutant gene product from a single allele is lethal.
The current paradigm for treating recessive genetic disorders has two primary dimensions: The first is a genetic construct, which is simply a normal copy of the gene or the information required to synthesize it in the cellular environment(Hawley, Lieu, Fong& Hawley, 1994). The second dimension is a delivery system capable of injecting the construct into the mutant cells. This delivery system is called a vector(Niidome& Huang, 2002). As such, somatic cell therapy is restricted by the ability to target specific cells, the delivery efficiency of vectors, the expression and durability of the inserted constructs, and safety.
The biological basis of gene therapy
Gene therapy has out grown the field of molecular biology. Life originatesfrom a single cell, making a cell the basic building block of all organisms. Human beings, for instance, comprise of trillions of cells with each cell having the ability to perform a unique function. The cells’ nucleus have a pairs of chromosomes each, these chromosomes carry the organism’s blueprint of life in codes, or genes(Niidome& Huang, 2002).
Researchers have always argued that presence of weaknesses in anorganism’s genes can cause hereditary diseases including hemophilia, sickle-cell anemia,and cystic fibrosis among others(Hawley, Lieu, Fong& Hawley, 1994). Correspondingly, having an extra or less chromosomes can result in conditions such as Down or Turnerssyndromes. As the study of heredities advanced, however, scientists have learnt that anpresence of altered genetic sequences can result in making individuals more susceptible to developing diseases such as schizophrenia, canceror atherosclerosis among others. Although these diseases have a genetic component, they are also predisposed to environmental factors including diet and way of life. The main aim of gene therapy is introduce corrected genes into an organism’s cells in order to replace the missing or dysfunctional cell protein thus treating hereditary diseases(Niidome& Huang, 2002).
The genes used for gene therapy can either be naturally-occurring genes which when used would produce the desired effect or they may be genetically manufactured or altered genes.Scientists have manipulated the structure of genes in the laboratory since the early 1970s through a process called gene splicing (Hawley, Lieu, Fong& Hawley, 1994). The process involves cutting a sequence of the genome with restriction enzymes, or proteins that act like molecular scissors. The ends where the DNA has been cut are sticky in the sense that they will easily bind to another sequence of DNA that was cut with the same enzyme. A DNA sequence and a gene sequence to be integrated in the DNA sequence can both be cut with the same type of enzyme and their ends will stick together(Niidome& Huang, 2002). The new DNA sequence will now have the gene inserted into it. The resulting product is called genetic engineered recombinant DNA.
There are basically two types of gene therapy. Germ-line gene therapy introduces genes into reproductive cells (sperm and eggs) or into embryos in order to correct genetic defects that could be passed on to future generations. Most of the current research, however, has been in the applications of somatic cell gene therapy (Niidome& Huang, 2002). In this type of gene therapy, therapeutic genes are inserted into tissue or cells to produce a naturally occurring protein or substance that is lacking or not functioning correctly in an individual patient. The main downside to this approach is that as each corrected cell dies, the therapeutic effects from gene therapy are lessened.
Scientific principles of Gene therapy
Genes are specific sequences of bases that encode instructions to make proteins. When genes are altered so that encoded proteins are unable to carry out their normal functions, genetic disorders can result. Gene therapy is designed to introduce genetic material into cells to compensate for abnormal genes or to make a beneficial protein. This article reviews the fundamentals in gene therapy and its various modes of administration with an insight into the role of gene therapy in Periodontics and future percepts and the technical and ethical issues of using gene therapy.
Genes that are present on the chromosomes form the basic unit of heredity. Genes are specific sequences of bases that encode instructions to make proteins(Hawley, Lieu, Fong& Hawley, 1994). A genetic disorder results when an alteration in the genes present on the chromosomes occur. Gene therapy is designed to introduce genetic material into cells to compensate for abnormal genes or to enable the making of a beneficial protein.
For correcting faulty genes, one of several approaches may be employed:
– A normal gene may be inserted into a nonspecific location within the genome to replace a nonfunctional gene; this is the most common approach.
- An abnormal gene may be swapped for a normal gene through homologous recombination.
- The abnormal gene could be repaired through selective reverse mutation, which returns the gene to its normal functional status.
- The regulation (the degree to which a gene is turned on or off) of a particular gene could be altered.
Gene therapy can target somatic (body) or germ (egg and sperm) cells. In somatic gene therapy the recipient’s genome is changed, but the change is not passed on to the next generation; whereas with germ line gene therapy the newly introduced gene is passed on to the offspring.
Germ line gene therapy is not being actively investigated, at least in larger animals and humans, although a lot of discussion is being conducted about its value and desirability.
Ethical issues surrounding gene therapy:
Because gene therapy involves making changes to the body’s set of basic instructions, it raises many unique ethical concerns. The ethical questions surrounding gene therapy include:
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- How can “good” and “bad” uses of gene therapy be distinguished?
- Who decides which traits are normal and which constitute a disability or disorder?
- Will the high costs of gene therapy make it available only to the wealthy?
- Could the widespread use of gene therapy make society less accepting of people who are different?
- Should people be allowed to use gene therapy to enhance basic human traits such as height, intelligence, or athletic ability.