从复制羊到复制人.ppt

?? Cloning ??從複製羊到複製人 Yu-Hui Tsai Ph.D. 台北醫學大學 醫學科學研究所 蔡郁惠 Cell Differentiation(??細胞分化??) In the field of biological sciences, there is a dogma that the expression state of genome in differentiated cells during the course of development, especially in the terminal differentiated cells, is irreversible. Cloning Plants from a Single Cell In plants, the ability of a differentiated cell to develop into a whole new individual is common. A single cell removed from carrot root and placed in culture medium may begin dividing and eventually grow into an adult plant. In this way, it is possible to propagate/clone large number of plants having desirable traits. Based on this data, it is evident that differentiation does not necessarily cause irreversible changes in genomic DNA. What is Cloning ? What is Cloning ? Cloning is a (new) biotechnological process involving injecting a diploid nucleus into an unfertilized, enucleated egg and allow it to develop up to blastocytes or a live new born. Cloning may be subdivided into : Therapeutic cloning : to produce stem cells for regenerative medicine Reproductive cloning : to create a body Frog In 1952, American embryologists Robert Briggs and Thomas King performed nuclear-transfer experiments with frog. They found that the number of embryos surviving to become tadpoles was smaller when donor cells were taken from animals at a more advanced developmental stage. Only 1 to 2 percent of embryos survived to become live offspring. Some of those clones that survive through birth die shortly afterward. Cloning for medicine Megan and Morage :clones of embryonic cells In 1995, Scientists at Roslin Institute near Edinburgh, Scotland, managed to produce Megan and Morage from cultured cells derived from a nine-day-old embryo. This made Megan and Morage clones of the embryo. Thus, partially differentiated cells can be genetically reprogrammed to function like those in an early embryo. Clones from cells of a matured animal In February 1997, D