The Bombay blood group is a rare group except in parts of India where a frequency of 1 in 7,600 has been observed. A high level of consanguinity has been observed among the parents of the Bombay phenotype(8). Individuals with the Bombay phenotype fail to express ANY A, B, or H antigen on their red cells or other tissues (8,39).

The cause of this antigenic absence is that the individuals produce no H glycosyl transferase ( FUT1). There is no H enzyme activity detected on the individuals red cells or in their serum.

These individuals may, however, posses either the A and / or the B gene on chromosome 9 and while an A or B glycosyl transferase may be produced there is no H antigen precursor that can be converted into either the A or B antigen (8, 39).

The cause of the Bombay phenotype is , predominately, mutation in the H gene on chromosome 19 that causes a non functional H glycosyl transferase to be produced. This is generally a Mendelian recessive gene. One cause identified has been a mutation that changes the code for trypsin at amino acid residue 316 of the transferase to that for a stop codon. The result is a truncated, non functional H transferase (8).

The serological characteristics are;

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I found an easy definition!

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then can it be called o negative

nope..
i thought someone will ask this question surely..
o negetive has also h antigen so no anti-h while bombay bloodgroup person have anti-h.

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can u explain it clearly .. o negative is so called because it has no A B ond H antigens on its surface.. please correct me if i am wrong

ABO blood groups do not consider the presence or absence of the H antigen.So by definition a person is defined as the O blood group if he has no A or B antigens on their surface.

Whie a person with the Bombay phenotype does not have the H antigen therefore will express the anti-H antibody.So on an ABO scaling these people will show up as O negative but will show a transfusion reaction when receiving O negative blood.They can only receive Bombay phenotype blood.

This is how i have understood it

it's not like that.

everyone with ABO bloodgroup has h antigen of RBC surface.
so they have not anti-h antibody.

while bombay group's[rare] individual have no h antigen also and antih,anti-a and anti-b antibody present.
hope basic idea of it you will get from my explanation.
it is hot favourite viva question in pathology.
check out here for details.

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What you are saying is true but my prof told me what i have written above.

Lolz.
it's k.
My proffesor told me right.

thanks. my doubt is cleared..