BCH Cloning readings
what are some of the ethical issues related to clones?
-Gene cloning is a carefully regulated technique that is largely accepted today and used routinely in many labs worldwide. -Reproductive cloning would present the potential of creating a human that is genetically identical to another person who has previously existed or who still exists. This may conflict with long-standing religious and societal values about human dignity, possibly infringing upon principles of individual freedom, identity and autonomy. However, some argue that reproductive cloning could help sterile couples fulfill their dream of parenthood or see it as a way to avoid passing on a deleterious gene that runs in the family without having to undergo embryo screening or embryo selection. -Therapeutic cloning, while offering the potential for treating humans suffering from disease or injury, would require the destruction of human embryos in the test tube.
types of artificial cloning
1. gene cloning 2. reproductive cloning 3.therapeutic cloning.
Why is it difficult to clone humans?
1. two proteins essential to cell division, known as spindle proteins, are located very close to the chromosomes in primate eggs. Consequently, removal of the egg's nucleus to make room for the donor nucleus also removes the spindle proteins, interfering with cell division. 2. In addition, some dyes and the ultraviolet light used to remove the egg's nucleus can damage the primate cell and prevent it from growing.
What are the potential applications of therapeutic cloning?
1.to grow healthy tissues in the laboratory that can be used replace injured or diseased tissues. 2. learn more about the molecular causes of disease by studying embryonic stem cell lines from cloned embryos derived from the cells of animals or humans with different diseases. 3.Finally, differentiated tissues derived from ES cells are excellent tools to test new therapeutic drugs.
1958
1958 - Nuclear transfer from a differentiated cell Frog John Gurdon Gurdon transplanted the nucleus of a tadpole intestinal cell into an enucleated frog egg. In this way, he created tadpoles that were genetically identical to the one from which the intestinal cell was taken. This experiment showed that 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
1975
1975 - First mammalian embryo created by nuclear transfer This experiment showed that mammalian embryos could be created by nuclear transfer. To show that the embryos could continue developing, Bromhall would have had to place them into a mother rabbit's womb. He never did this experiment.
1987
1987 - Nuclear transfer from embryonic cell Cow This experiment added cows to the list of mammals that could be cloned by nuclear transfer. Still, mammalian cloning was limited to using embryonic cells as nuclear donors. Cloning using nuclei from differentiated adult somatic cells still wasn't thought possible.
1996
1996 - Nuclear transfer from laboratory cells Sheep Ian Wilmut and Keith Campbell This experiment showed that cultured cells can supply donor nuclei for cloning by nuclear transfer. this experiment showed that it might be possible to use such modified cells to create transgenic animals—such as cows that could make insulin for diabetics in their milk.
1997
1997 - First primate created by embryonic cell nuclear transfer monkey This experiment showed that primates, humans' closest relatives, can be cloned.
2001
2001 - Endangered animals cloned by somatic cell nuclear transfer Gaur and Mouflon A challenge to cloning endangered and extinct species is finding closely related animals to serve as egg donors and surrogates. The gaur and mouflon were chosen in part because they are close relatives of domestic cattle and sheep, respectively. 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.
1902
Artificial embryo twinning in a vertebrate Salamander embryos from a more-complex animal can also be "twinned" to form multiple identical organisms—but only up to a certain stage in development.
1996
Dolly: First mammal created by somatic cell nuclear transfer Sheep 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.
1984
First mammal created by nuclear transfer This experiment showed that it was possible to clone a mammal by nuclear transfer—and that the clone could fully develop.
1952
First successful nuclear transfer Frog 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.
1885
First-ever demonstration of artificial embryo twinning with a Sea urchin Hans Adolf Edward Dreisch: 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.
2013
Human embryonic stem cells created by somatic cell nuclear transfer
what animals have been cloned?
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. 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, horse, mule, ox, rabbit and rat. In addition, a rhesus monkey has been cloned by embryo splitting.
1998-1999
More mammals cloned by somatic cell nuclear transfer Mice, cows, and goats Multiple groups 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.
do cloned animals always look identical?
No. Clones do not always look identical. Although clones share the same genetic material, the environment also plays a big role in how an organism turns out. ex: Cc and inactivation of X chromosome The distribution of X inactivation, which seems to occur randomly, determines the appearance of the cat's coat.
1997
Nuclear transfer from genetically engineered laboratory cells Sheep 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.
2007
Primate embryonic stem cells created by somatic cell nuclear transfer Rhesus monkey Researchers took a cell from an adult monkey and fused it with an enucleated egg cell. This experiment showed that nuclear transfer in a primate was possible. It opened the door to the possibility of human therapeutic cloning
What are the potential drawbacks of cloning animals?
Reproductive cloning is a very inefficient technique and most cloned animal embryos cannot develop into healthy individuals. very low efficiency, combined with safety concerns, Researchers have observed some adverse health effects in sheep and other mammals that have been cloned. Another potential problem centers on the relative age of the cloned cell's chromosomes. As a consequence, clones created from a cell taken from an adult might have chromosomes that are already shorter than normal, which may condemn the clones' cells to a shorter life span.
1928
The cell nucleus controls embryonic development Salamander 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.
What is therapeutic cloning?
Therapeutic cloning involves creating a cloned embryo for the sole purpose of producing embryonic stem cells with the same DNA as the donor cell. These stem cells can be used in experiments aimed at understanding the disease and developing new treatments for disease. Stem cells are harvested from cloned embryos at this stage of development, resulting in the destruction of the embryo while it is still in the test tube.
do clones occur naturally?
Yes!!!! some plants and bacteria, produce genetically identical offspring through asexual reproduction. Natural clones, also known as identical twins
asexual reproduction
a new individual is generated from a copy of a single cell from the parent organism.
What sort of cloning research is going on at NHGRI?
at National Human Genome Research Institute (NHGRI) Gene cloning is the most common type of cloning r
What are the potential drawbacks of therapeutic cloning?
concerned about the striking similarities between stem cells and cancer cells. Both cell types have the ability to proliferate indefinitely and some studies show that after 60 cycles of cell division, stem cells can accumulate mutations that could lead to cancer ---Therefore, the relationship between stem cells and cancer cells needs to be more clearly understood
cloning
genetically identical copies of a biological entity. same genetic makeup as the original
have humans been cloned?
human cloning still appears to be fiction In 1998, scientists in South Korea claimed to have successfully cloned a human embryo but said the experiment was interrupted very early In 2002, Clonaid, part of a religious group that believes humans were created by extraterrestrials. Clonaid never provided any evidence to confirm the existence of this clone or the other 12 human clones it purportedly created. In 2004, Seoul National University in South Korea published a paper in the journal Science in which it claimed to have created a cloned human embryo in a test tube. However, an independent scientific committee later found no proof to support the claim and, in January 2006, paper redacted
how are genes cloned?
insert a gene from one organism, often referred to as "foreign DNA," into the genetic material of a carrier called a vector. (Examples of vectors include bacteria, yeast cells, viruses or plasmids) vector is placed in laboratory that prompt it to multiply,
what are the potential applications of cloned animals?
potential benefits for the fields of medicine and agriculture. Scottish researchers have cloned other sheep that have been genetically modified to produce milk that contains a human protein essential for blood clotting Another possible use of cloned animals is for testing new drugs and treatment strategies. The great advantage of using cloned animals for drug testing is that they are all genetically identical, which means their responses to the drugs should be uniform rather than variable as seen in animals with different genetic make-ups. Another application is to create clones to build populations of endangered, or possibly even extinct, species of animals. In 2001, researchers produced the first clone of an endangered species:
therapeutic cloning
procedures embryonic stem cells for experiments aimed to creating tissue to replace injured or diseased tissues same technique as reproductive cloning
gene cloning
produce copies of genes or segments of DNA different process than reproductive and therapeutic cloning
reproductive cloning
produces copies of whole animals same technique as therapeutic cloning
how are animals cloned?
take a mature somatic cell and transfer the DNA of the donor animal's somatic cell into an egg cell, Researchers can add the DNA from the somatic cell to the empty egg in two different ways. 1. they remove the DNA-containing nucleus of the somatic cell with a needle and inject it into the empty egg. 2.they use an electrical current to fuse the entire somatic cell with the empty egg. the egg is allowed to develop into an early-stage embryo in the test-tube and then is implanted into the womb of an adult female animal.
identical twins occur
when a fertilized egg splits, creating two or more embryos that carry almost identical DNA. Identical twins have nearly the same genetic makeup as each other