| Remarque : ceci est un travail scolaire. Il n'a pas de caution scientifique, médicale ou autre, et, bien que cet élève ait fait un travail qui a été accepté dans le contexte scolaire, il ne peut prétendre être une source fiable d'informations ! |
BOTTERON Philippe 3Sb
Biologie 5 décembre 1999
Résumé du rapport sur la mucoviscidose Rapport complet
Cystic fibrosis is a genetic disease, it is therefore transmitted only from parents to their children. The disease is on chromosome 7, and as it is transmitted in a recessive way, it is necessary that the two parents carry the defective gene. To be carrying gene means of two genes to have reached one. If the two parents carry it, they have one chance out of four to have a child who has inherited it. Moreover, half of their offspring will be carrying the disease, even if it does not show. In Europe, a newborn baby out of 2000 develops it, and one person out of 20 carries the disease. Thanks to the progress already carried out in the field of remedies against the cystic fibrosis, one achieves now at an exceptional expectancy. Now most patients live over 31 years of age. Cystic fibrosis is due to an anomaly in the cells producing mucus. It blocks the respiratory tracts and unlike the mucus of a healthy person, it does not make it possible to evacuate dust and pathogenic agents.
For more than sixty years, studies were carried out on this disease, which condemns - almost - everybody who suffers from it. Already in 1938 at the university of Columbia Dorothy Andersen described the symptoms of cystic fibrosis and the anomalies due to this disease with precision. In 1946, one started to study the hereditary factors of cystic fibrosis. But it's only in these ten last years that one has made fulgurating progress by discovering a method to identify genes.
We studied the genetic therapy treatment. This principle consists of introducing into the cells a piece of normal gene, which will replace the defective one. Several means to introduce this gene were tested, but none is really perfectly effective for the moment. One of the methods tested consists of transplanting a healthy gene into an adenovirus (which has a predilection for respiratory tracts), which was, of course, weakened in order to prevent it from starting the disease, which it usually causes. Another virus, whose name is adeno-associated virus, resembles the adenovirus much. It is not known to give diseases to humans. Its great characteristic is that it needs another virus (like the adenovirus) to grow normally. The potential advantages of this vector are its great safety and its integration in the human genome, which would appear through a gene expression transferred later on. The last vector is the liposome. One introduces a plasmid there (strand of ADN). This liposome will be stuck to the cellular wall, will amalgamate and pour its contents inside the cell. The influenza is thus avoided, even if the integration of the corrected genetic material is easier when the vector is viral.
Another dimension studied is to know if one can modify a human gene. Within the framework of the cure of such a disease, yes. But how to differentiate a good cause from a bad one? In the case the foetus of a woman is affected by cystic fibrosis, it would be normal to abort it.
But what would occur if the parents wished to get rid of a child only carrying the gene, but not feeling their effects, this in order to avoid problems for the future generations? These ethical problems also deserve thinking about.
