|
Interessanter Artikel zum Thema klonen und warum es bisher so oft fehlgeschlagen ist. Es scheint so das man Erwachsene Stammzellen zwar klonen kann aber nur zu begrenzter Lebensspanne führt,so nach dem Motto °Klone ich einen 35 jährigen Mann und dieser Mann verstirbt sagen wir mal mit 70 Jahren an eines natürlichen Todes so kann dessen Klon auch nur etwa 35 Jahre alt werden da die Lebensuhr der Zellen die geklont wurden ja schon 35 Jahre lebten. So verstehe ich das zumindest was auch erklärt warum Dolly nicht nur nicht alt werden konnte sie wurde eingeschläfert weil es einfach keinen Sinn mehr machte sie am Leben zu halten und sie schon in frühen Jahren an "Missbildungen" erkrankte. Study Sheds Light on Why Cloning So Often Fails Fri Apr 4, 4:04 PM ET Add Health - Reuters to My Yahoo! By Jacqueline Stenson NEW YORK (Reuters Health) - The vast majority of attempts at animal cloning are a failure and it may be because certain genes necessary for early development are not activated in the process, new study findings suggest. In the cloning procedure that created Dolly the sheep and other cloned mammals, researchers extract the nucleus of an adult cell from an animal that is to be cloned and insert it into an egg that has been stripped of its own nucleus. If everything goes as planned, a very early embryo known as a blastocyst results, is transferred into the womb of a female and grows into a clone of the adult. But the process fails the vast majority of the time. In mice, only 1 to 3 percent of blastocysts develop to full-term offspring, and fewer survive to adulthood, said Dr. Rudolf Jaenisch, a professor of biology at the Whitehead Institute for Biomedical Research and the Massachusetts Institute of Technology (news - web sites), both in Cambridge. By comparison, he said, up to a third of clones created using an embryo-derived stem cell instead of an adult cell survive to birth. The question is what accounts for the difference. Embryonic stem cells are derived from a developing embryo and have the ability to grow into any cell type in the body. To date, researchers have isolated embryonic stem cells from mice and humans only, Jaenisch noted. In a new study published in the journal Development, Jaenisch and colleagues compared normal mouse blastocysts to those cloned from adult cells or embryonic stem cells. The researchers were looking for the expression of a gene called Oct4, which is essential for normal embryonic development, and 10 other genes that appear to function similarly. All 11 genes were properly expressed in the normal blastocysts and the ones cloned from embryonic stem cells, results showed. But among the blastocysts cloned from adult cells, just 62% expressed all 11 genes. "This argues that the faulty reprogramming that one sees in cloning is caused by the inability of the clone to activate those silent genes," Jaenisch told Reuters Health. These genes, already at work in a normally developing embryo or one cloned from embryonic stem cells, have long been inactivated in adult cells, he explained. The findings raise the issue of whether researchers can find ways to turn these inactivated genes back on, he said. But this research is just part of the story of how to more efficiently clone animals, Jaenisch noted, because hundreds of genes are not correctly expressed in clones, creating problems during development and throughout life. Scientists are seeking to clone healthy animals for a variety of reasons. Some wish to create herds of animals that have been genetically altered to produce therapeutic milk or organs for human transplant, for example, and others are hoping to save endangered species. SOURCE: Development 2003;130:1673-1680. |
|
| aus der Diskussion: | Geron mit Hammernews!! |
| Autor (Datum des Eintrages): | meislo (05.04.03 22:36:48) |
| Beitrag: | 82 von 3,090 (ID:9093266) |
| Alle Angaben ohne Gewähr © wallstreetONLINE | |