Antigen absent in Bombay blood group-
**Core Concept**
The Bombay blood group is a rare blood type characterized by the absence of the H antigen on red blood cells. This is due to a genetic mutation that affects the production of the H antigen, making individuals with this blood type unable to produce ABO blood group antigens.
**Why the Correct Answer is Right**
The H antigen is a precursor to the ABO blood group antigens and is essential for their production. In individuals with the Bombay blood group, the mutation leads to a deficiency in the enzyme fucosyltransferase, which is necessary for the synthesis of the H antigen. As a result, the H antigen is absent on the surface of red blood cells, making it impossible to produce A and B blood group antigens. This unique characteristic makes the Bombay blood group a fascinating area of study in transfusion medicine.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the H antigen is not a type of ABO blood group antigen, but rather a precursor to these antigens.
**Option B:** This option is incorrect because the absence of the H antigen does not affect the production of Rh blood group antigens.
**Option C:** This option is incorrect because the Bombay blood group is not associated with the Kell blood group system.
**Clinical Pearl / High-Yield Fact**
The Bombay blood group is also known as the "Oh" blood group, and individuals with this blood type are considered to be extremely rare, with only a few reported cases worldwide.
**Correct Answer:** D. The H antigen.