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Related to Bombay phenotype: recessive epistasis
Etymology: Bombay, India, where first reported
a rare genetic trait in which there is no expression of the A, B, or H antigens on the red blood cells. Bombay phenotypes (genetically hh) lack the H gene which normally produces the H antigen, a precursor for A and B antigens. Since H is not expressed, A or B cannot be expressed. The serum contains anti-A, anti-B, and anti-H. See also ABO blood group.
Physiology For A or B antigens to be expressed on RBCs, the cells must have a precursor substance—H antigen encoded by the H gene; Oh type RBCs do not agglutinate with antisera containing anti-A, anti-B, or anti-H type antibodies as they lack the H gene, and ergobstance; Oh subjects do have anti-A, anti-B, and anti-H antibodies in their serum, which may cause problems when cross-matching donors and recipients