Dolly
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Who was Dolly the sheep?
Dolly, a female Finn Dorset sheep born in 1996 and deceased in 2003, holds the distinction of being the first clone of an adult mammal. This groundbreaking achievement was made by British developmental biologist Ian Wilmut and his team at the Roslin Institute in Scotland.
Dolly's creation involved a technique called somatic cell nuclear transfer (SCNT). Scientists fused a mammary gland cell from an adult Finn Dorset ewe with an unfertilized egg cell, whose nucleus had been removed. This fusion resulted in the mammary cell nucleus transferring into the egg cell, which then started to divide.
The announcement of Dolly's birth in February 1997 sparked considerable ethical debate about the potential uses and misuses of mammalian cloning technology.
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Why is Dolly the sheep famous?
Dolly the sheep is famous because she was the first clone of an adult mammal, born in 1996 at the Roslin Institute in Scotland. This achievement, led by British developmental biologist Ian Wilmut and his colleagues, demonstrated that adult mammalian cells could be used to create a clone, which overturned previous scientific assumptions. Dolly's creation involved somatic cell nuclear transfer (SCNT), where the nucleus of a mammary gland cell from an adult Finn Dorset ewe was transferred into an unfertilized egg cell that had its own nucleus removed. The resulting cell was stimulated to divide and then implanted into a surrogate ewe. Dolly's birth sparked ethical debates about the potential uses and misuses of cloning technology.
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What does it mean that Dolly was a cloned sheep?
Dolly the sheep, born in 1996, was the first mammal cloned from an adult somatic cell using a technique called somatic cell nuclear transfer (SCNT).
SCNT involves transferring the nucleus of a somatic (body) cell into an enucleated egg (an egg cell that has had its own nucleus removed). The egg cell is then stimulated to divide, and the resulting embryo is implanted into a surrogate mother. Dolly was created from a mammary gland cell taken from an adult Finn Dorset ewe.
Dolly's birth dispelled the presumption that adult mammals could not be cloned and ignited debate about the potential uses and misuses of cloning technology. Some scientists argue that cloning farm animals could allow livestock farmers to breed only high-quality animals.
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How was Dolly the sheep cloned?
Dolly the sheep was the first mammal cloned from an adult cell. Scientists at the Roslin Institute used somatic cell nuclear transfer (SCNT), a refined version of nuclear transfer, to create her.
The SCNT process involves taking an egg cell from one sheep and removing its nucleus. Then, the nucleus from a mammary gland cell of another sheep is injected into the enucleated egg cell. With electrical stimulation, the mammary cell nucleus fuses with the egg cell and begins to divide. The resulting cluster of cells is implanted into a surrogate ewe's uterus, where it develops into a lamb genetically identical to the sheep that donated the mammary cell.
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What scientific technique was used to create Dolly?
Dolly the sheep was created using a scientific technique called somatic cell nuclear transfer (SCNT). This process involves taking the nucleus from a somatic (body) cell of one sheep and transferring it into an egg cell of another sheep that has had its own nucleus removed. After the transfer, the egg is stimulated to divide and develop into an embryo, which is then implanted into a surrogate mother to be carried to term. Dolly was the first mammal to be cloned from an adult cell using this technique.
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Why was the cloning of Dolly considered important for science and medicine?
The cloning of Dolly the sheep in 1996 was a watershed moment because it proved that adult mammals could be cloned, overturning previous assumptions. Dolly was created through somatic cell nuclear transfer (SCNT), where the nucleus of an adult mammary gland cell was transferred into an enucleated egg cell.
Dolly's successful cloning had two major implications:
* Scientific advancement It demonstrated that the DNA of adult cells could be reprogrammed to create a whole organism, which had previously been considered impossible.
* Medical possibilities It opened the door to new research avenues in stem cell research and regenerative medicine, offering potential treatments for diseases and new ways to breed livestock.6 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Dolly, female Finn Dorset sheep that lived from 1996 to 2003, the first clone of an adult mammal, produced by British developmental biologist Ian Wilmut and colleagues of the Roslin Institute, near Edinburgh, Scotland. The announcement in February 1997 of Dolly’s birth marked a milestone in science, dispelling decades of presumption that adult mammals could not be cloned and igniting a debate concerning the many possible uses and misuses of mammalian cloning technology.
The concept of mammalian clones, even humans, was not new at the time of Dolly’s birth. Among mammals, naturally occurring genetic clones, or individuals genetically identical to one another, had long been recognized in the form of monozygotic (identical) twins. Unlike Dolly, however, such clones are derived from a single zygote, or fertilized egg, and thus they are clones of one another, rather than clones of another individual. Moreover, clones had been generated previously in the laboratory, but only from embryonic cells that were either undifferentiated or only partially differentiated. In animals, the production of clones from fully differentiated (adult) cells (e.g., skin or muscle cells) had been carried out successfully only in lower species, such as frogs.
For decades, scientists had tried and failed to clone mammals from existing adults. The repeated failures led scientists to speculate about the significance of the timing and process of cell differentiation in the developing mammalian embryo. Of particular interest were changes that occurred to DNA during an animal’s development, whereby patterns in gene expression were altered as cells became increasingly specialized in function. It was realized that, through the process of differentiation, adult mammalian cells lose totipotency—the ability to become any of the different cell types required for making a complete and viable animal. It was presumed that the process was irreversible. The successful production of Dolly, however, proved otherwise.
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Dolly was cloned from a mammary gland cell taken from an adult Finn Dorset ewe. Wilmut and his team of researchers at Roslin created her by using electrical pulses to fuse the mammary cell with an unfertilized egg cell, the nucleus of which had been removed. The fusion process resulted in the transfer of the mammary cell nucleus into the egg cell, which then began to divide. In order for the mammary cell nucleus to be accepted and functional within the host egg, the cell first had to be induced to abandon the normal cycle of growth and division and enter a quiescent stage. To accomplish that, researchers deliberately withheld nutrients from the cells. The importance of the step had been determined experimentally, though an explanation for its necessity was lacking. Nevertheless, starting with a collection of mammary cell nuclei and host egg cytoplasms derived from Scottish Blackface ewes, a number of fused couplets successfully formed embryos. The reconstructed embryos were transferred to surrogate Scottish Blackface ewes. Of 13 recipient ewes, one became pregnant, and 148 days later, which is essentially normal gestation for a sheep, Dolly was born.
Dolly remained alive and well long after her birth, with a functional heart, liver, brain, and other organs, all derived genetically from the nuclear DNA of an adult mammary gland cell. The technique used to produce her later became known as somatic cell nuclear transfer (SCNT). SCNT has since been used to generate a wide variety of mammalian clones, from different types of adult cells; its success in producing clones of primates, however, has been notably limited.
On February 14, 2003, Dolly was euthanized by veterinarians after being found to suffer from progressive lung disease. Her body was preserved and displayed at the National Museum of Scotland in Edinburgh.