Previous Video Dolly- the sheep, produced in was the first clone of an adult animal, but several other species have been cloned since, including dogs and cats. The most common method of cloning adult animals is somatic cell nuclear transfer. First the nucleus is removed from an egg's cell, then a somatic cell such as a skin cell is taken from the animal to be cloned.
The nucleus containing chromosomal DNA is removed and injected into the egg. The egg is stimulated to divide by chemical or electrical treatment, and forms an embryo, which is implanted into the uterus of an adult female, where it continues to develop until birth. The resulting clone has identical chromosomal DNA to the original animal, but the mitochondrial DNA is often different since the mitochondria come from the cytoplasm of the egg, usually from a different individual.
Also phenotypic differences between the clone and the original can occur due to environmental and epigenetic factors during development. Just as identical twins are slightly different from each other, despite having the same DNA. Reproductive cloning is the process of producing a genetically identical copy—a clone—of an entire organism. While clones can be produced by splitting an early embryo—similar to what happens naturally with identical twins—cloning of adult animals is usually done by a process called somatic cell nuclear transfer SCNT.
In SCNT, an egg cell is taken from an animal and its nucleus is removed, creating an enucleated egg. Then a somatic cell—any cell that is not a sex cell—is taken from the animal to be cloned.
The nucleus of the somatic cell is then transferred into the enucleated egg—either by direct injection or by fusion of the somatic cell to the egg using an electrical current. The egg now contains the nucleus, with the chromosomal DNA, of the animal to be cloned. It is stimulated to divide, forming an embryo, which is then implanted into the uterus of a surrogate mother.
If all goes well, it develops normally and the clone is born. Although this process has been used to successfully clone many different types of animals—including sheep, cows, mules, rabbits, and dogs—its success rate is low, with only a small percentage of embryos surviving to birth.
Cloned animals that survive to birth also appear to age and die prematurely. This is because their DNA comes from adult cells that have undergone telomere shortening—loss of a small portion of the protective ends of chromosomes with each cell division—as part of the normal aging process. While the chromosomal DNA of the clone is the same as that of the nucleus donor, it may have different mitochondrial DNA, since the mitochondria come from the cytoplasm of the egg cell, which is usually from a different animal.
Also, phenotypic differences can occur between the clone and the original animal, due to environmental and epigenetic factors. For example, the first cloned cat, Cc, looked very different from the original cat, because the coat pattern is due to random X-chromosome inactivation in different cells.
Despite the technical challenges, reproductive cloning has many potential uses including the production of genetically identical research animals, livestock with desired traits, and offspring of endangered species. It even has potential applications in human infertility and disease, although cloning of humans has not yet been done, and would raise ethical concerns.
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Login processing Legal issues aside, some major organizations advise against human reproductive cloning on ethical grounds. Because of the low success rate for reproductive cloning and the likely health complications of cloned individuals, physicians from the American Medical Association and scientists with the American Association for the Advancement of Science publicly advised against human reproductive cloning.
Additionally, religious groups raise other ethical concerns, such as the idea that reproductive cloning is "playing God. Human cloning is not yet possible, but cloning technology is taking small steps in that direction. Much cloning research is actually focused on creating embryonic stem cells from the cloned embryo, rather than growing cloned humans this field is called therapeutic cloning and is less controversial than reproductive cloning.
Recently, scientists at the New York Stem Cell Foundation Laboratory were able to create a developing cloned embryo, from which they were able to derive a self-reproducing line of embryonic stem cells.
However, they did so without first removing the egg cell's, so the embryo was actually abnormal and had an additional set of chromosomes. Live Science. Joseph Castro. When a colony of bacteria containing a gene of interest is located, the bacteria can be propagated to make millions of copies of the plasmids. Then, the plasmids can be extracted for gene modification and transformation. Gene modification, or gene design, is when a genetic engineer cuts the gene apart and replaces regions of it with new material.
Transformation is the step in which the new genetic material is transferred to a new organism, which changed it genetically. The organism, such as a plant, is grown, and the seeds they produce have inherited the new genetic properties.
In reproductive cloning, a genetic engineer removes a mature somatic cell any cell except for reproductive cells from an organism and transfers the DNA into an egg cell that has had its own DNA removed, according to the NHGRI. Then, the egg is jump-started chemically to start the reproductive process. Finally, the egg is implanted into the uterus of a female of the same species as the egg.
The mother gives birth to an animal that has the same genetic makeup as the animals that donated the somatic cell. This was the process that produced Dolly the sheep. Therapeutic cloning works in a similar way to reproductive cloning.
A cell is taken from an animal's skin and is inserted into the outer membrane of a donor egg cell. Then, the egg is chemically induced so that it creates embryonic stem cells. These stem cells can be harvested and used in experiments aimed at understanding diseases and developing new treatments. The first study of cloning took place in , when German scientist Hans Adolf Eduard Driesch began researching reproduction. In , he was able to create a set of twin salamanders by dividing an embryo into two separate, viable embryos, according to the Genetic Science Learning Center.
Since then, there have been many breakthroughs in cloning. In , British biologist John Gurdon cloned frogs from the skin cells of adult frogs.
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