Question

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Describe ABO and Rh blood typing and the basis and significance of cross-reactions?

Answer 1

ABO blood group :- In human, ABO blood group system is found. It is a very classical example of the multiple alleles. When more than two different forms of a given gene exist in a species , they are reffered to as multiple alleles.

In human, if the RBCs has the antigen on its surface , then the blood group of individual is A blood group.

If people has antigen B , then blood group is B.

If people has both antigen A and B , then blood group is AB.

If non of the antigen is present on the RBCs , then it is called O blood group.

The alleles  I^a and I^b are responsible for the production of the A and B antigens. Both I^a and I^b are completely dominant to the allele i, which fails to specify A and B antigen. But when allele A and B are present together, they will express both.

It is a very unusal type of the blood group system because the have the antibodies prior to the exposure to antigen.

So they also have the antibodies agaist the particular antigen present in the blood. Accordingly , the plasma of type A blood grouo contains anti -B antibodies. B type has anti- A antibodies, AB has no antibody, O has both the anti bodies.

Rh blood group:- It was discoverd by landsteiner and Wiener in 1940. It is based on the Rh antigen on the plasma membrane of the RBC. It was named so because it was first dicovered in the rhesus monkey, Macacus rhesus. The Rh antigens are located on two Rhesus proteins- RhD and RhCE- encoded by two highly polymorphic genes, RHD and RHCE and it will express only in the RBCs.RhD protein carries the D antigen and RhCE protein carries CE antigens in varies combination.

Based on Rh antigen, blood grop are of two type

Rh positive :- if D antigen is present on the individuals RBCs.

Rh negative:- if D antigen is absent on the individuals RBCs.

Rh positive is more common.

Significance of the Blood group system:-

The ABO and Rh blood group has a very common significance in determining the blood group of children, in paternal disputes, clinical significance , in criminal case, in graft rejection, in erythroblastosis fetalis etc.

The Rh antigen has a particular significance when Rh negative mother gives birth to the Rh positive child. It is a condition called as the erthroblastosis fetalis.it is a figure of ABO blood group system.