Clones - Clones Scottish scientists at Roslin Institute created the much-celebrated sheep"Dolly Science magazine as the breakthrough of 1997

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Clones Scottish scientists at Roslin Institute created the much-celebrated sheep "Dolly" Science magazine as the breakthrough of 1997; generated uncertainty over the meaning of "cloning" Three types of cloning (1) recombinant DNA technology or DNA cloning, (2) reproductive cloning, and (3) therapeutic cloning. Recombinant DNA Technology or DNA Cloning The terms "recombinant DNA technology" "DNA cloning” "molecular cloning," and "gene cloning" all refer to the same process: the transfer of a DNA fragment of interest from one organism to a self-replicating genetic element such as a bacterial plasmid. The DNA of interest can then be propagated in a foreign host cell. This technology has been around since the 1970s, and it has become a common practice in molecular biology labs today. Scientists studying a particular gene often use bacterial plasmids to generate multiple copies of the same gene. Plasmids are self-replicating extra-chromosomal circular DNA molecules, distinct from the normal bacterial genome (see image to the right). Plasmids and other types of cloning vectors were used by Human Genome Project researchers to copy genes and other pieces of chromosomes to generate enough identical material for further study. To "clone a gene," a DNA fragment containing the gene of interest is isolated from chromosomal DNA using restriction enzymes and then united with a plasmid that has been cut with the same restriction enzymes. When the fragment of chromosomal DNA is joined with its cloning vector in the lab, it is called a "recombinant DNA molecule." Following introduction into suitable host cells, the recombinant DNA can then be reproduced along with the host cell DNA. Plasmids can carry up to 20,000 bp of foreign DNA. Besides bacterial plasmids, some other cloning vectors include viruses, bacteria artificial chromosomes (BACs), and yeast artificial chromosomes (YACs). Cosmids are artificially constructed cloning vectors that carry up to 45 kb of foreign DNA and can be packaged in lambda phage particles for
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infection into E. coli cells. BACs utilize the naturally occurring F-factor plasmid found in E. coli to carry 100- to 300-kb DNA inserts. A YAC is a functional chromosome derived from yeast that can carry up to 1 MB of foreign DNA. Bacteria are most often used as the host cells for recombinant DNA molecules, but yeast and mammalian cells also are used. Reproductive Cloning Reproductive cloning is a technology used to generate an animal that has the same nuclear DNA as another currently or previously existing animal. Dolly was created by reproductive cloning technology. In a process called "somatic cell nuclear transfer" (SCNT), scientists transfer genetic material from the nucleus of a donor adult cell to an egg whose nucleus, and thus its genetic material, has been removed. The reconstructed egg containing the DNA from a donor cell must be treated with chemicals or electric current in order to stimulate cell division. Once the cloned embryo
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This note was uploaded on 09/01/2009 for the course BIO bio taught by Professor Mrkim during the Spring '09 term at Saddleback.

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Clones - Clones Scottish scientists at Roslin Institute created the much-celebrated sheep"Dolly Science magazine as the breakthrough of 1997

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