Reproductive Cloning
THE HISTORY
OF REPRODUCTIVE CLONING
5000 B.C.
"Humans discover that they can improve corn crops by planting seeds from the best plants."
1800s
The father of genetics, Gregor Mendel, establishes the basic laws of inheritance.
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"Johann Friedrick Miescher extracts what comes to be known as DNA from the nuclei of white blood cells."
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"August Weissmann states genetic information of a cell diminishes with each cell division."
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1900s
Herbert Webber coins the world clone to refer to “any group of cells or organisms produced asexually from a single sexually produced ancestor.”
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"Hans Spemann performs first nuclear transfer experiment using salamander embryos."
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"Briggs and King clone frogs by using nuclear transfer."
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Dolly, the first animal cloned from adult cells, is born
2000s
"Britain becomes the first country to grant a patent for cloned early-stage human embryos."
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Scientists cloned pigs with the hopes of it being able to be used for human organ transplants.
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Later, a goat, sheep, ox, cat, rabbit, cow, horse, deer, African wildcat, and dog were cloned.
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"Chromatin transfer (CT) technology, is developed and exclusively licensed for pet cloning.
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1902 - Artificial Embryo Twinning in a Vertebrate
"Spemann’s first challenge was to figure out how to split the two cells of an embryo much stickier than sea urchin cells.Each cell grew into an adult salamander. Spemann also tried to divide more advanced salamander embryos using this method, but he found that cells from these embryos weren’t as successful at developing into adult salamanders.This experiment showed that embryos from a more-complex animal can also be “twinned” to form multiple identical organisms—but only up to a certain stage in development."
1952 - First Successful Nuclear Transfer
"Briggs and King transferred the nucleus from an early tadpole embryo into an enucleated frog egg (a frog egg from which the nucleus had been removed). Most importantly, this experiment showed that nuclear transfer was a viable cloning technique. It also reinforced two earlier observations. First, the nucleus directs cell growth and, ultimately, an organism’s development. Second, embryonic cells early in development are better for cloning than cells at later stages."
1996 - First Mammal Created by Somatic Cell Nuclear Transfer
"Of 277 attempts, only one produced an embryo that was carried to term in a surrogate mother. This famous lamb, named Dolly, brought cloning into the limelight. Her arrival started conversations about the implications of cloning, bringing controversies over human cloning and stem cell research into the public eye."
1997 - Nuclear Transfer From Genetically Engineered Laboratory Cells
"This experiment showed that sheep could be engineered to make therapeutic and other useful proteins in their milk, highlighting the potential medical and commercial uses for cloning."
2001 - Endangered Animals Cloned by Somatic Cell Nuclear Transfer
"As the list of successfully cloned animals grew, scientists began to explore cloning as a way to create animals belonging to endangered or extinct species. In 2009, using goast as egg donors and surrogates, another group of researchers cloned the first extinct animal, a Spanish mountain goat called the bucardo. Sadly, the one kid that survived gestation died soon after birth due to a lung defect."
2013 - Human Embryonic Stem Cells Created by Somatic Cell Nuclear Transfer
"Overcoming decades of technical challenges, Mitalipov and colleagues were the first to use somatic cell nuclear transfer to create a human embryo that could be used as a source of embryonic stem cells. The resulting stem cell lines were specific to the patient they came from, a baby with a rare genetic disorder.In this experiment, researchers took a skin cell from the patient and fused it with a donated egg cell. Following the cloning controversy of 2004–2005, in which South Korean scientists falsely claimed to have used somatic cell nuclear transfer to create embryonic stem cell lines, the scientific community demanded much stronger evidence that the procedure had actually been successful.
1885 - Artificial Embryo Twinning
"Dreisch showed that by merely shaking two-celled sea urchin embryos, it was possible to separate the cells. Once separated, each cell grew into a complete sea urchin.
This experiment showed that each cell in the early embryo has its own complete set of genetic instructions and can grow into a full organism."
1928-Cell Nucleus Controls Embryonic Development
"Spemann temporarily squeezed a fertilized salamander egg to push the nucleus to one side of the cytoplasm. Essentially the first instance of nuclear transfer, this experiment showed that the nucleus from an early embryonic cell directs the complete growth of a salamander, effectively substituting for the nucleus in a fertilized egg."
1958 - Nuclear Transfer from a Differentiated Cell
"Gurdon transplanted the nucleus of a tadpole intestinal cell into an enucleated frog egg. This experiment showed that, despite previous failures, nuclei from somatic cells in a fully developed animal could be used for cloning. Importantly, it suggested that cells retain all of their genetic material even as they divide and differentiate (although some wondered if the donor DNA came from a stem cell, which can differentiate into multiple types of cells)."
1997 - First Primate Created by Embryonic Cell Nuclear Transfer
"Primates are good models for studying human disorders. Cloning identical primates would decrease the genetic variation of research animals, and therefore the number of animals need in research studies.This experiment showed that primates, humans’ closest relatives, can be cloned."
1998-1999 - More Mammals Cloned by Somatic Cell Nuclear Transfer
"After the successes leading up to Dolly and Polly, other scientists wanted to see if similar techniques could be used to clone other mammalian species. Before long, several more animals had been successfully cloned. Among them were transgenic animals, clones made from fetal and adult cells, and a male mouse; all previous clones had been female."
2007 - Primate Embryonic Stem Cells Created by Somatic Cell Nuclear Transfer
"This experiment showed that nuclear transfer in a primate, which researchers had tried for years without success, was possible. It opened the door to the possibility of human therapeutic cloning: creating individual-specific stem cells that could be used to treat or study diseases."
