|MadSci Network: Development|
There are a very large number of humans that have been 'created' in vitro in the sense that the fertilization of an egg cell by a sperm cell occurred in vitro. Since 1981, 45,000 babies have been born in the US using in vitro fertilization. Please see: http://www.asrm.com/Patients/FactSheets/invitro.html http://www.fertilethoughts.net/faq/asrm/invitro.html Mice are routinely created that are derived from embryonic stem cells. In this case, the embryonic stem cells have been modified genetically to produce mice of interest to researchers in which a specific gene has been knocked out. The part of this process that applies to your question is the technique used to get live mice from the embryonic stem cells, which are grown in tissue culture. Once a line of genetically modified mouse stem cells has been identified, they are used to make mouse embryos by incorporating the cells into a chimeric embryo in which the other cells are those of a mouse blastocyst, typically from a strain with a different coat color. (A chimera is a creature from mythology that has a snake for a tail, a lion's head and body, and a goat's head in the midsection. Biologists now use this word to represent an animal containing cells from two different strains or even two different species.) The mixed embryo is implanted into a foster mother and is born as a mouse made up of two different cell types: the stem cells and the blastocyst cells. If the germ line of the chimeric mouse include cells derived from the stem cells, the mouse will produce at least some progeny whose genes are derived from the stem cells when it is bred. There is a cartoon of this process at: http://www.ri.bbsrc.ac.uk/molbiol/mcwhir/embryoni.htm This process, if applied to humans, would produce a chimeric individual having some cells derived from the stem cells and some cells derived from the blastocyst cells. The chimeric blastocyst would have to be implanted in a foster mother, just as embryos from IVF are implanted today. It is not possible to bring a human embryo, or any other mammalian embryo, to term in vitro; a foster mother must be used. Although this experiment could be carried out today, there is absolutely no reason to do so, as there could not possibly be any benefit to the individual created in this way. There would be no benefit to society, and no advancement of scientific knowledge, by carrying out such an experiment. You might also be interested to learn that it is possible to create embryos that are wholly derived from a donor cell that need not be a stem cell. This is the process popularly referred to as cloning. So far, sheep, mice, cattle, pigs and goats have been cloned. It would certainly be possible to clone a human, but this experiment is also regarded as unethical, because there is a risk that the individual would not be normal, and there wouldn't be any benefit to anyone or to society in general from doing this. Please see the following answers in the MadSci archive for further information on cloning: http://www.madsci.org/posts/archives/mar2001/984508482.Ge.r.html http://www.madsci.org/posts/archives/feb2001/981130372.Ge.r.html http://www.madsci.org/posts/archives/990482242.Cb.r.html http://www.madsci.org/posts/archives/988822002.Ge.r.html You might find the MGI Glossary useful in understanding this answer: http://www.informatics.jax.org/userdocs/glossary.shtml Thank you for an interesting question. Yours, Paul Szauter Mouse Genome Informatics
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