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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,Further development,1.definition of cloning,Cloning,creating,a,copy,of,living matter,such as a cell or organism.The copies produced through cloning have identical genetic makeup and are known as clones.Many organisms in nature reproduce by cloning.Scientists use cloning techniques in the laboratory to create copies of cells or organisms with valuable traits.Their work aims to find practical applications for cloning that will produce advances in medicine,biological research,and industry.,2.HOW SCIENTISTS CLONE CELLS,A.Blastomere Separation,In,blastomere,separation,scientists fertilize an egg cell with a sperm cell in a laboratory dish.The resulting embryo is allowed to divide until it forms a mass of about four cells.Scientists remove the outer coating of the embryo and place it in a special solution that causes the individual cells of the embryo,known as blastomeres,to separate.Scientists then put each blastomere in culture,where it forms an embryo containing the same genetic makeup as the original embryo.Each new embryo can then be implanted into the uterus of a surrogate mother to develop during a normal pregnancy.,B.Blastocyst Division,In,blastocyst,division,scientists allow a fertilized egg to divide until it forms a mass of about 32 to 150 cells,known as a blastocyst.Scientists then split the blastocyst in two and implant the two halves into the uterus of a surrogate mother.The two halves develop as identical twins.,C.Somatic Cell Nuclear Transfer,While,blastomere,separation and blastocyst division produce animals containing the genetic material from both a mother and father,somatic cell nuclear transfer produces an animal carrying the genetic material of only one parent.In this technique,scientists transfer the genetic material from a donor,s somatic cell(any body cell other than an egg or sperm cell)to an enucleated egg cell,that is,an egg cell with its nucleus,and thus its genetic material,removed.The resulting cloned cell contains the genetic material of the donor,s somatic cell.,Genetic Engineering,Genetic engineering enables scientists to produce clones of cells or organisms that contain the same genes.1.Scientists use restriction enzymes to isolate a segment of deoxyribonucleic acid(DNA)that contains a gene of interest,for example,the gene regulating insulin production.2.A plasmid removed from a bacterium and treated with the same restriction enzyme binds with the DNA fragment to form a hybrid plasma.3.The hybrid plasmid is re-inserted back into the bacterium,where it replicates as part of the cell,s DNA.4.A large number of identical daughter cells(clones)can be cultured and their gene products extracted for human use.,First Cloned Cat,The worlds first cat clone,named CC,for carbon copy or courtesy copy,was produced by scientists at Texas A&M University in College Station.Born December 22,2001,the kitten was cloned using a method called nuclear transfer,in which nuclei from cells of an adult animal are inserted into egg cells with nuclei removed.The embryos that result are then implanted into the uterus of a surrogate mother,where they develop in a normal pregnancy.,Identical Calves,Two of eight calves cloned from cells obtained from one adult cow stand in a field in Ishikawa,Japan.The calves were cloned by researchers at Kinki University in Nara,Japan.The results of the cloning experiment were published in 1998.,
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