Blood type is determined by the presence or absence of a sugar decoration present on the surface of Red Blood cells. It is not only found on Red Blood cells but on the vascular system as well on clotting factors such as von Willebrand factor (vWF).
The gene that generates this sugar decoration (formally called gylcosolation) is the ABO gene. ABO gene encodes for a protein that is a gylcosal-transferase. This means the ABO gene encoded for a protein that transfers sugars to a protein. This protein is encoded by yet another gene call FUT1. The FUT1 protein is the foundation of all the blood types, it is the building block that the sugars A or B are attached. This is a simplistic model of the construction for A, B but it will suffice.
Blood types are classified basically as combinations of the ABO phenotypes.
There are four major blood groups determined by the presence or absence of two antigens – A and B – on the surface of red blood cells:
Group A – has only the A antigen on red cells (and B antibody in the plasma)
Group B – has only the B antigen on red cells (and A antibody in the plasma)
Group AB – has both A and B antigens on red cells (but neither A nor B antibody in the plasma)
Group O – has neither A nor B antigens on red cells (but both A and B antibody are in the plasma)
There are very specific ways in which blood types must be matched for a safe transfusion.
This blood group is quite rare with an incidence of 1 in 250,000.The reason behind it’s unique name is the association of this disease with the city Bombay. This blood phenotype was first discovered in Bombay, now known as Mumbai, in India, by Dr. Y.M. Bhende in 1952.
The Bombay blood type, h/h or Oh is present in less than 0.0004% of the world’s population.
First discovered in 1952 by Dr. Y G Bhide, the Bombay Blood type is largely recognised as the rarest blood group in the world. In an observation of the blood type’s reaction with the commonly recognised blood phenotypes, it was found that the Bombay Blood type contained a previously unknown antigen – H.
Antigens A and B are both found to be made from antigen H. So, people with the Bombay phenotype can donate blood but not serve as recipients.
The Bombay phenotype is allowed to donate red blood cells to any of the blood types within the ABO phenotype realm, the reverse, however, is not possible. People with the Bombay phenotype can only receive blood from their own group because of the antigen reactions that may cause defects in the receiver’s immunology.
If you are lookng for Bombay Blood Group, it is quite likely that the required units are not available in any Blood Bank
The Bombay phenotype is usually found within close knit communities.
With as many as 0.01% of people from Mumbai who could be carrying the Bombay phenotype, the rare blood type is usually the result of both parents carrying a recessive allele which will result in the child having the h/h blood group. Close knit communities, or even inbreeding, seem to be the cause of the blood type.