|MadSci Network: Genetics
The classic Bombay phenotype has only been reported in those of Indian descent. It is quite rare with an incidence of 1 in 250,000. The bombay phenotype is characterized by mutations in fucosyltransferase. Fucosyltransferase is an enzyme that adds sugars to molecules exposed on the red blood cell surface. These sugars are used to determine the ABO blood type. Therefore a person with Bombay has the phenotype of O blood even though genetically they might have a different blood type. Since these are independent those with Bombay blood type are not necessarily one blood type (they could be any). There are similar phenomena to Bombat phenotype. There is a para-Bombay phenotype in which the fucosyltransferase levels are greatly reduced. This occurs in Chinese individuals with a frequency of 1 in 8,000. Also the bombay phenotype is one of many elements of Rambam-Hasharom which is a genetic syndrome also characterized by mental retardation. IT is thought the genetic lesion here is quite large.
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