Yoga Is Good for You. But Is It Medicine? A procedure in which damaged tissues or organs are repaired or replaced with genetically identical cells that originate from undifferentiated stem cells. Published by Houghton Mifflin Company. The production of embryonic stem cells for use in replacing or repairing damaged tissues or organs, achieved by transferring a diploid nucleus from a body cell into an egg whose nucleus has been removed.
The stem cells are harvested from the blastocyst that develops from the egg, which, if implanted into a uterus, could produce a clone of the nucleus donor. All rights reserved. FDA jurisdiction includes human cells used in therapy involving the transfer of genetic material by means other than the union of gamete nuclei. Examples of such genetic material include, but are not limited to: cell nuclei for cloning , oocyte nuclei, ooplasm, which contains mitochondria and genetic material contained in a genetic vector, transferred to gametes or other cells.
Any clinical research involving these techniques would require an IND. However, in , a moratorium on United States federal funding for SCNT prohibits funding the practice for the purposes of research.
Thus, though legal, SCNT cannot be federally funded. Mitochondrial replacement techniques MRT are novel procedures where maternal nuclear DNA is transferred from her oocyte or zygote to a donor oocyte from which the nuclear DNA has been removed. In FDA requested that the Institute of Medicine IOM produce a consensus report regarding the ethical and social policy issues related to genetic modification of eggs and zygotes to prevent transmission of mitochondrial disease 1.
The report concluded that MRT in humans is ethically permissible as long as certain conditions and principles are met. Over time, the telomeres become so short that the cell can no longer divide and, consequently, the cell dies. This is part of the natural aging process that seems to happen in all cell types.
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. Indeed, Dolly, who was cloned from the cell of a 6-year-old sheep, had chromosomes that were shorter than those of other sheep her age. Dolly died when she was six years old, about half the average sheep's year lifespan. 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 disease and developing new treatments for disease. To date, there is no evidence that human embryos have been produced for therapeutic cloning. The richest source of embryonic stem cells is tissue formed during the first five days after the egg has started to divide. At this stage of development, called the blastocyst, the embryo consists of a cluster of about cells that can become any cell type.
Stem cells are harvested from cloned embryos at this stage of development, resulting in destruction of the embryo while it is still in the test tube. Researchers hope to use embryonic stem cells, which have the unique ability to generate virtually all types of cells in an organism, to grow healthy tissues in the laboratory that can be used replace injured or diseased tissues. In addition, it may be possible to 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.
Finally, differentiated tissues derived from ES cells are excellent tools to test new therapeutic drugs. Many researchers think it is worthwhile to explore the use of embryonic stem cells as a path for treating human diseases. However, some experts are 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 if stem cells are to be used to treat human disease. Gene cloning is a carefully regulated technique that is largely accepted today and used routinely in many labs worldwide.
However, both reproductive and therapeutic cloning raise important ethical issues, especially as related to the potential use of these techniques in humans. 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.
Others see human cloning 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.
Consequently, opponents argue that using this technique to collect embryonic stem cells is wrong, regardless of whether such cells are used to benefit sick or injured people. Cloning Fact Sheet. Do clones ever occur naturally? What are the types of artificial cloning? How are genes cloned? How are animals cloned? What animals have been cloned? Have humans been cloned? Do cloned animals always look identical?
What are the potential applications of cloned animals? What are the potential drawbacks of cloning animals? What is therapeutic cloning? What are the potential applications of therapeutic cloning?
What are the potential drawbacks of therapeutic cloning? What are some of the ethical issues related to cloning?
0コメント