Genetic engineering and Gene therapy

It is the stuff of science fiction: tailor-made babies with exceptional intelligence and stunning looks. How close are we to this reality? Genetic knowledge is indeed rapidly expanding, but most research centers around understanding the content and function of the human genome; less applies to the manipulation of human genetic material. In other words, we need to first learn more about the natural function of genetic information, before we can learn how to alter it. The engineering of an entire organism is still a very distant possibility. Even the manipulation of a single gene, as therapy for a genetic disorder, has not yet been successfully achieved.

Genetic engineering and Gene therapy have the same basic premise: the introduction of specific new genetic material into an organism's genome. There are many variations on the technology to achieve this goal, depending on the organism and situation. The basic strategy is to place the new genetic material (for example, a gene for a new desired function) into the cell, and use the cell's natural machinery to integrate this material into the genome. vector - A vector is a small piece of DNA used to carry a gene of interest. Besides the gene being studied, a vector may contain elements which are used to help the gene integrate into a genome. recombination - The process in which strands of DNA are cut open and rejoined. This is done by a complex of proteins called DNA recombinase. Recombination can be used to integrate the DNA from a vector into an organism's genome.

Genetic Engineering

Genetic engineering refers to the deliberate design of an entire organism. The process involves altering the genetic material of a single cell in a very small developing embryo, which then develops into an entire organism, with the altered genetic material in every cell.

There are many questions raised by the possibility of genetic engineering in humans; for example, whether it is ethical to value some genetic traits over other and what those traits might be. There are also concerns about the consequences of altering a few select genes, since genes interact in very complex ways, and we may not be able to predict all the consequences of any specific manipulation.

Genetically engineered plant products, which, for example, grow more quickly or are more resistant to disease, are quite common today. However, plant cells are, not surprisingly, very different from those of humans. First, the nature of plant genetics makes it easier to insert and remove genes from the genome. In addition, plant seeds are accustomed to being exposed to harsh environmental conditions. Thus, plant cells can be relatively easily manipulated in the laboratory and then used to grow genetically modified crops. Genetic manipulation of some laboratory animals, such as flies and mice, is also routinely used in research.

In contrast, the technology available to manipulate human genes and embryos is not well developed. The human genome is unusually resistant to manipulation, so we currently do not have technology with allows the efficient removal and insertion of genes in human cells. Also, if it were ever to be done, human genetic engineering would have to be carried out on a zygote or very small embryo in a laboratory. Because the normal environment of a developing human embryo in the womb is very sheltered and controlled, the embryos are extremely sensitive to any handling. Currently, very small human embryos are handled in infertility clinics and in limited cases of screening for genetic disease. Even with the aid of powerful drugs and implantation of multiple embryos, the survival rate in these cases is still quite low. Given the difficulties in manipulation of human genes and the delicate nature of human embryos, our technology is far from being able to produce a genetically engineered human.

Despite the limitations in our current technical abilitiy to manipulate embryos, the ethical and moral questions raised are both fascinating and important. If and when the technology to engineer human embryos becomes available, we hope to have explored the many possible ramifications, so that we can regulate and apply genetic engineering in a thoughtful and safe manner.

Gene Therapy

Gene therapy refers to the process of changing human genetic material to repair or compensate for the effects of a mutation or abnormality. For example, a gene therapy for a single gene disorder might aim to replace the mutated copy of the gene with a normal one. Because gene therapy aims to alter only some cells in an individual (those affected by the genetic condition), and because it seeks primarily to relieve the suffering of disease, there are generally less ethical objections. Nonetheless, there are still questions about the possible consequences of manipulating a few genes which may interact in complex ways with many others. In addition, there may be detrimental effects of the method used to introduce the therapeutic genes. For example, modified viruses are common vectors used in experimental gene therapy.

Although there is a great deal of research and experimentation in this area, there are, at this time, no cases of successful, lasting, gene therapy treatments. The main barriers to gene therapy are a) access to the affected tissues and b) as discussed above, the challenges of manipulating the human genome. We learned that human embryos do not react well to handling in the laboratory, and it is similarly difficult to manipulate other human tissues, because they generally cannot survive outside the body (nor can the body survive without them!). Even when this barrier can be overcome, as in the case of accessible cells like blood cells (e.g. for anemia) and lung surfaces (e.g. for Cystic Fibrosis), it is a great challenge to make human cells accept engineered DNA. In some experimental cases, it has been possible to introduce genes into cells for therapy, but the effects have always been temporary, because the cells react by turing off the altered genes or cutting them out of the genome.

Research in gene therapy is moving forward, and there are many promising new approaches being investigated. They are all theoretical or experimental at this time, and have not been proven clincally. While the future will likely bring some successful ways of treating disease by fixing mutated genes or compensating for their dysfuntion, the lesson of years of research is that it is extremely difficult to alter human genetic information, even in very limited ways.

The current state of technology makes genetic engineering impossible and gene therapy still an evolving hope for the future. This does not mean that the ethical questions raised by genetic engineering and gene therapy are not worth discussing. Rather, we are fortunate to have the opportunity to explore these issues and, hopefully, form thoughtful policies and beliefs regarding gene therapy and genetic engineering, before technology makes these procedures a reality. However, it is also important to remain calm and informed about the difference between science fiction and science fact.

Note: Human genetics is an extremely complex topic. This website is meant only as an introduction and overview. If you are concerned about how genetics may affect your health, always consult your physician.