What animals have been cloned?
Cloning animals has not been controversial. So far sheep, goats, pigs, cows, mice, rabbits, horses and cats have been cloned. But cloning is still not easy to do, and researchers haven’t been able to clone monkeys, and until recently, human embryos. Korean scientists reporting in a February 2004 edition of Science magazine were able to clone a human embryo and harvest stem cells from it. A first in human cloning, the embryo survived through the blastocyst stage, but was not implanted in a woman. (Blastocysts are a hollow ball of about a hundred cells from which stem cells can be obtained.) For reasons that are little understood, many cloned embryos do not develop properly. They die before or shortly after birth. It’s also clear that cloned animals that grow to adulthood may have unexpected defects, such as heart or respiratory problems that do not appear until later in life. Listen to a Science Friday discussion on problems detected in cloned animals.
Hundreds of cloned animals exist today, but a number of different species is limited. Scientists have been cloning animals for many years. Before dolly, the first mammal cloned from the cell of an adult animal was created from embryonic cells. Since this time, researchers have cloned a number of large animals including sheep, goats, cows, mice, pigs, cats, rabbits, and gaur. Attempts of cloning certain species such a monkeys, chickens, horses, and dogs have been unsuccessful. Some species may be more resistant to somatic cells nuclear transfer than others. The process of stripping the nucleus from an egg cell and replacing it with nucleus of a donor cell is traumatic one, and improvements in cloning technologies may be needed before many species can be cloned successfully. Notably, the most infamous animal cloned has been the Dolly the Sheep. Dolly was the first mammal to be cloned from adult DNA. It took 277 cloning attempts to create Dolly who was created February 24, 1997 in Edinbur
Scientists have been cloning animals for many years. In 1952, the first animal, a tadpole, was cloned. Before the creation of Dolly, the first mammal cloned from the cell of an adult animal, clones were created from embryonic cells. Since Dolly, researchers have cloned a number of large and small animals including sheep, goats, cows, mice, pigs, cats, rabbits, and a gaur. See Cloned Animals below. All these clones were created using nuclear transfer technology. Hundreds of cloned animals exist today, but the number of different species is limited. Attempts at cloning certain species have been unsuccessful. Some species may be more resistant to somatic cell nuclear transfer than others. The process of stripping the nucleus from an egg cell and replacing it with the nucleus of a donor cell is a traumatic one, and improvements in cloning technologies may be needed before many species can be cloned successfully.
Over the last 50 years, scientists have conducted cloning experiments in a wide range of animals using a variety of techniques. In 1979, researchers produced the first genetically identical mice by splitting mouse embryos in the test tube and then implanting the resulting embryos into the wombs of adult female mice. Shortly after that, researchers produced the first genetically identical cows, sheep and chickens by transferring the nucleus of a cell taken from an early embryo into an egg that had been emptied of its nucleus. It was not until 1996, however, that researchers succeeded in cloning the first mammal from a mature (somatic) cell taken from an adult animal. After 276 attempts, Scottish researchers finally produced Dolly, the lamb from the udder cell of a 6-year-old sheep. Two years later, researchers in Japan cloned eight calves from a single cow, but only four survived. Besides cattle and sheep, other mammals that have been cloned from somatic cells include: cat, deer, dog, h
