Ireneparalegal
08-15-2005, 08:14 PM
I tried to find the best article for everyone to read and comprehend. Basically it is a genetic defect (?) where two embryos start out as twins, but during the pregnancy, they fuse together. Meaning, one human being. No, not a hermaphrodite. One individual that carries two different DNA. There was a documentary on The Learning Channel called "I am my own Twin". A woman was accused of fraud and kidnapping because her biological children's DNA did not match her DNA even though she had given birth to them. The fraud aspect came about when she tried to apply for assistance and a blood test is required so that no one can claim children that are not biologically/legally theirs. She was accused of "using" someone else's kids to obtain assistance. After a lengthy two years, she was vindicated when she was found to have "Chimerism". The judge that ruled in her favor made a comment regarding how many other folks have "Chimerism" and are being freed by DNA that shows they are innocent? Or how many fathers are being told they are NOT the biological father of a child, when in fact he may in fact be? Scary thing to think about especially with criminals.
Natural chimerism
Chimerism may occur naturally during pregnancy, when two non-identical twins (even of different sexes) combine in the womb at a very early stage of development, such as that of the blastocyst, to form a single organism. Such an organism is called a tetragametic chimera as it is formed from four gametes — two eggs and two sperm.
As the organism develops, the resulting chimera can come to possess organs that have different sets of chromosomes. For example, the chimera may have a liver composed of cells with one set of chromosomes and have a kidney composed of cells with a second set of chromosomes. This has occurred in humans, though it is considered extremely rare, but since it can only be detected through DNA testing, which itself is currently rare, it may be more common than currently believed. As of 2003, there were about 30 human cases in the literature, according to New Scientist.
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Research chimerism
In biological research, chimeras are artificially produced by mixing cells from two different organisms. This can result in the eventual development of an adult animal composed of cells from both donors, which may be of different species — for example, in 1984 a chimeric geep was produced by combining embryos from a goat and a sheep. A chicken with a quail's brain has been produced by grafting portions of a quail embryo into a chicken embryo.
In August 2003, researchers at the Shanghai Second Medical University in China reported that they had successfully fused human skin cells and rabbit eggs to create the first human chimeric embryos. The embryos were allowed to develop for several days in a laboratory setting, then destroyed to harvest the resulting stem cells. Increasingly realizable projects using part-human, part-animal chimeras as living factories for producing cells or organs raise a host of ethical and safety issues.
Chimeras should not be confused with hybrids, which are organisms formed from two gametes (each from a different species) which formed a single zygote. All cells in a hybrid originate from this single zygote. For example, a mule is a hybrid created from the sperm of a donkey and the egg of a horse.
Chimeras should also not be confused with mosaics, which are organisms with genetically different cell types, but which again originate from a single zygote.
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See also
Natural chimerism
Chimerism may occur naturally during pregnancy, when two non-identical twins (even of different sexes) combine in the womb at a very early stage of development, such as that of the blastocyst, to form a single organism. Such an organism is called a tetragametic chimera as it is formed from four gametes — two eggs and two sperm.
As the organism develops, the resulting chimera can come to possess organs that have different sets of chromosomes. For example, the chimera may have a liver composed of cells with one set of chromosomes and have a kidney composed of cells with a second set of chromosomes. This has occurred in humans, though it is considered extremely rare, but since it can only be detected through DNA testing, which itself is currently rare, it may be more common than currently believed. As of 2003, there were about 30 human cases in the literature, according to New Scientist.
[edit]
Research chimerism
In biological research, chimeras are artificially produced by mixing cells from two different organisms. This can result in the eventual development of an adult animal composed of cells from both donors, which may be of different species — for example, in 1984 a chimeric geep was produced by combining embryos from a goat and a sheep. A chicken with a quail's brain has been produced by grafting portions of a quail embryo into a chicken embryo.
In August 2003, researchers at the Shanghai Second Medical University in China reported that they had successfully fused human skin cells and rabbit eggs to create the first human chimeric embryos. The embryos were allowed to develop for several days in a laboratory setting, then destroyed to harvest the resulting stem cells. Increasingly realizable projects using part-human, part-animal chimeras as living factories for producing cells or organs raise a host of ethical and safety issues.
Chimeras should not be confused with hybrids, which are organisms formed from two gametes (each from a different species) which formed a single zygote. All cells in a hybrid originate from this single zygote. For example, a mule is a hybrid created from the sperm of a donkey and the egg of a horse.
Chimeras should also not be confused with mosaics, which are organisms with genetically different cell types, but which again originate from a single zygote.
[edit]
See also