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Transcript of cloning
Dolly, the first mammal to be cloned from adult DNA, was put down by lethal injection Feb. 14, 2003. Dolly had been suffering from lung cancer and crippling arthritis. Most Finn Dorset sheep live to be 11 to 12 years of age, an examination of Dolly indicated that, other than her cancer and arthritis, she appeared to be quite normal. The sheep from which Dolly was cloned died several years before she was created. Dolly was a mother to six lambs, bred the old-fashioned way. The terms recombinant DNA technology, DNA cloning, molecular cloning and gene cloning all refer to the same process: transfer of a DNA fragment from one organism to a self-replicating genetic
element, for example, a bacterial plasmid. The DNA can then be propagated in a foreign host cell. This has been around since the 1970s, and it has become a wekk-known 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. Plasmids and other types of cloning vectors were used by Human Genome Project researchers to copy genes and other pieces of chromosomes to generate identical material for further studies. To "clone a gene," a DNA fragment containing the gene 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. The recombinant DNA can then be reproduced along with the host cell DNA. Plasmids can carry up to 20,000 bp of foreign DNA. Other than plasmids, other cloning vectors include: viruses, bacteria artificial chromosomes (BACs), and yeast artificial chromosomes (YACs). Cosmids are an artificially constructed cloning vector that carry up to 45 kb of foreign DNA. BACs utilizes the naturally occurring F-factor plasmid found in E. coli to carry 100- to 300-kb DNA inserts. A YAC is a functional chromosome obtained from yeast that can carry up to 1 MB of foreign DNA. Bacteria is most often used as host cells for recombinant DNA molecules, however, yeast and mammalian cells are used as well. Reproductive Cloning Dolly, or any other animal created using nuclear transfer technology is not actually an identical clone. Only the clone's chromosomal or nuclear DNA is the same. Some of the clone's genetic materials come from the mitochondria in the cytoplasm of the enucleated egg. Mitochondria, which are organelles that serve as power houses to the cell, contain their own small segments of DNA. Mitochondrial DNA is believed to play an important role in the aging process. How can cloning technologies be used? Recombinant DNA technology is important when learning about other related technologies, such as: gene therapy, genetic engineering of organisms, and sequencing genomes. Gene therapy can be used to treat specific genetic conditions by introducing virus vectors that carry correct copies of faulty genes into the cells of an organism. Genes from different organisms that improve taste and nutritional value or provide resistance to certain types of disease can be used to genetically engineer food crops. Reproductive cloning could also be used to re-
populate endangered animals or animals that are difficult to breed. In 2001, the first cloned endangered animal was born, a wild ox called Gaur. Gaur died from an infection about 48 hours after birth. In 2001, scientists in Italy reported the successful cloning of a healthy baby mouflon, an endangered sheep. .Other endangered species that are potential candidates for cloning include the African bongo antelope, the Sumatran tiger, and the giant panda. Cloning extinct animals is a much greater challenge because the egg and the surrogate needed to create the cloned embryo would be of a species different from the clone. Therapeutic cloning technology may be used in humans to produce whole organs from single cells or to produce healthy cells that will replace the damaged cells in degenerative diseases. Much work still needs to be done before therapeutic cloning can become a realistic option for treatment. What are the risks of cloning? -Reproductive cloning is expensive and highly inefficient.
-More than 90% of cloning attempts fail to produce viable offspring.
- More than 100 nuclear transfer procedures would be required to produce one clone.
-Cloned animals tend to have more compromised immune function and higher rates of infection, tumor growth, and other disorders.
- Many cloned animals have not lived long enough to generate good data about how clones age.
-Appearing healthy at a young age unfortunately is not a good indicator of long-term survival. -
Clones tend to die mysteriously.
(Australia's first cloned sheep appeared perfectly healthy on the day she died. The results of her autopsy failed to determine a cause of death) In 2002, researchers at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, reported that the genomes of cloned mice are compromised. In analyzing more than 10 000 liver and placenta cells of cloned mice, they discovered that about 4% of genes function abnormally. The abnormalities do not arise from mutations in the genes but from changes in the normal activation or expression of certain genes. Problems also may result from programming errors in the genetic material from a donor cell. When an embryo is created from the union of a sperm and an egg, the embryo receives copies of most genes from both parents. A process called "imprinting" chemically marks the DNA from the mother and father so that only one copy of a gene (either the maternal or paternal gene) is turned on. Defects in the genetic imprint of DNA from a single donor cell may lead to some of the developmental abnormalities of cloned embryos. http://en.wikipedia.org/wiki/Cloning
http://www.invitrogen.com/site/us/en/home/References/an-introduction-to-cloning-a-researchers-guide-to-cloning-dna.html Bibliography: Recombinant DNA Technology or DNA Cloning Reproductive cloning is a technology used to create an animal that has the same nuclear DNA as another preexisting animal. Dolly was created by reproductive cloning technology. In a process called, somatic cell nuclear transfer (SCNT), scientists transfered genetic material from the nucleus of a donor adult cell to an egg's nucleus, and thus its genetic material, had 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 reaches a suitable stage, it's transferred to the uterus where it continues to develop until birth. (Diagram)