A blood transfusion will also temporarily give a person cells from someone else, but in a bone marrow transplant, the new blood cells are permanent, according to the Tech Museum of Innovation in San Jose, California. But in other cases, the recipient may have a mix of both their own blood cells and donor ones, according to a 2004 review paper in the journal Bone Marrow Transplantation. In some cases, all of the blood cells in a person who received a bone marrow transplant will match the DNA of their donor. This means that a person with a bone marrow transplant will have blood cells, for the rest of their life, that are genetically identical to those of the donor, and are not genetically the same as the other cells in their own body. Bone marrow contains stem cells that develop into red blood cells. During such transplants, which can be used for example to treat leukemia, a person will have their own bone marrow destroyed and replaced with bone marrow from another person. The mystery was solved when doctors discovered that Keegan was a chimera-she had a different set of DNA in her blood cells compared to the other tissues in her body.Ī person can also be a chimera if they undergo a bone marrow transplant. But the tests suggested that genetically, Keegan could not be the mother of her sons. For example, in 2002, news outlets reported the story of a woman named Karen Keegan, who needed a kidney transplant and underwent genetic testing along with her family, to see if a family member could donate one to her. These individuals often don't know they are a chimera. The remaining fetus will have two sets of cells, its own original set, plus the one from its twin. This can occur with fraternal twins, if one embryo dies very early in pregnancy, and some of its cells are "absorbed" by the other twin. One way that chimeras can happen naturally in humans is that a fetus can absorb its twin. But chimeras aren't always man-made-and there are a number of examples of human chimeras that already exist.Ī chimera is essentially a single organism that's made up of cells from two or more "individuals"-that is, it contains two sets of DNA, with the code to make two separate organisms. The news that researchers want to create human-animal chimeras has generated controversy recently, and may conjure up ideas about Frankenstein-ish experiments.
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