克隆技术【英文】

Cloning Molecules and Cells


DNA makes a copy when it replicates to make two molecules A cell divides by mitosis to make two identical daughter cells.
Cloning Mammals



In 1997 Ian Wilmut and colleagues in Scotland announced the birth of “Dolly” the first cloned mammal. In a procedure similar to Gurdon’s, called somatic cell nuclear transfer, the lab group removed the nuclei from cells in the mammary gland of a sheep and placed them in enucleated eggs of another sheep. This link shows images of somatic cell nuclear transfer (http://www.advancedcell.com/scnt.htm)
CLONING
Lecture Notes for Biotechnology
What is Cloning?


To most people, the term “cloning” means making a copy of an individual. In biology, cloning can have different uses depending on what is being copied.
Cloning Organisms


Botanists and home gardeners have been cloning plants for centuries – take a “cutting” or piece of a plant and put in soil and it will form a new plant. Animals that reproduce by asexual reproduction, such as small female freshwater crustaceans, produce offspring which are genetic copies of the mother
Cloning Vertebrate Animals


In the 1960’s, John Gurdon experimented with a technique called nuclear transplantation He destroyed the nuclei of unfertilized eggs of the African clawed toad with UV light and replaced them with nuclei taken from intestinal cells of tadpoles of the same species
CC the Kitten



Click on the link below to see Copy Cat (CC) the cloned kitten (Nature, 2002) CC has a different coat coloration, so she is not identical to the nucleus donor http://www.nature.com/nature/journal/ v415/n6874/fig_tab/nature723_F1.html
Other Cloned Mammals



Since Dolly, other mammal species have been successfully cloned. These include cow, goat, cat, pig, mule and gaur. In many of these attempts, such as the one producing CC the kitten, the donor nucleus is not removed from its cell but the donor cell is fused with an enucleated egg.
Dolly (cont)
Baidu Nhomakorabea

The eggs were stimulated to begin dividing by treating them with either chemicals or electricity Some of the eggs starting cleaving and were placed in the uteruses of other sheep. Only one attempt of 277 was successful, producing Dolly.
Dolly (cont)


Dolly developed lung cancer and arthritis and was euthanized in 2003 at the age of 6 years. Most sheep of Dolly’s breed live to 11 or 12 years.
Gurdon (cont)


A small percentage of the eggs with the transplanted nuclei developed past the cleavage stage into tadpoles and adults Later experiments using the transplanted nuclei from adult toad skin, kidney, heart and lung cells produced the same results