7/3/2023 0 Comments Genetic chimera![]() Each population of cells keeps its own character and the resulting organism is a mixture of tissues. Innate chimeras are formed from at least four parent cells (two fertilised eggs or early embryos fused together). If the different cells have emerged from the same zygote, the organism is called a mosaic. ![]() Animals Īn animal chimera is a single organism that is composed of two or more different populations of genetically distinct cells that originated from different zygotes involved in sexual reproduction. The term genetic chimera has been used at least since the 1944 article of Belgovskii. While German dermatologist Alfred Blaschko described Blaschko's lines in 1901, the genetic science took until the 1930s to approach a vocabulary for the phenomenon. For example, transplantation of bone marrow often determines the recipient's ensuing blood type. Īnother way that chimerism can occur in animals is by organ transplantation, giving one individual tissues that developed from a different genome. In contrast, an individual where each cell contains genetic material from two organisms of different breeds, varieties, species or genera is called a hybrid. Normally, genetic chimerism is not visible on casual inspection however, it has been detected in the course of proving parentage. In plant chimeras, however, the distinct types of tissue may originate from the same zygote, and the difference is often due to mutation during ordinary cell division. Animal chimeras are produced by the merger of two (or more) embryos. In animals and human chimeras, this means an individual derived from two or more zygotes, which can include possessing blood cells of different blood types, subtle variations in form ( phenotype) and, if the zygotes were of differing sexes, then even the possession of both female and male sex organs. All rights reserved.A genetic chimerism or chimera ( / k aɪ ˈ m ɪər ə, k ə-/ ky- MEER-ə, kə-) is a single organism composed of cells with more than one distinct genotype. More multidisciplinary research is required for a better understanding of this fascinating subject.īlood chimeras Fusion chimeras Human natural chimeras Microchimeras.Ĭopyright © 2020 The Author. If human chimeras are more common than hitherto thought there could be many medical, social, forensic, and legal implications. To date there are no examples in humans of twin chimeras involving germ cells. In marmoset monkey twins the exchange via the placenta is not limited to blood but can involve other tissues, including germ cells. Blood chimeras are formed by blood transfusion between dizygotic twins via the shared placenta and are more common than was once assumed. Only 28 of the 50 individuals with a 46,XX/46,XY karyotype were either true hermaphrodites or had ambiguous genitalia. Even sex-discordant chimeras can have a normal male or female phenotype. Many are discovered accidently, for example, during a routine blood group test. ![]() Most chimeras remain undetected, especially if both zygotes are of the same genetic sex. Two zygotes can fuse together during an early embryonic stage to form a fusion chimera. Fetal and maternal cells can cross the placental barrier so that both mother and child may become microchimeras. Natural chimeras can arise in various ways. ![]() The first human chimera was reported in 1953. This review concerns natural human chimeras. Recipients of tissue and organ transplants are artificial chimeras. A chimera is an organism whose cells are derived from two or more zygotes. The term chimera has been borrowed from Greek mythology and has a long history of use in biology and genetics.
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