An control the specificity, and this can be

An entire blood group system that
consists of one or more erythrocyte antigens describes the term ‘blood group’, a
series of genes control the specificity, and this can be allelic or linked
close on a single chromosome making it difficult to distinguish it from

The absence of specific antigens
can be the bases of blood separation, consideration of a blood group could be
by any detected variation or polymorphism detected in the blood. However, the
term blood group is usually restricted to blood cells, surface antigens, and
generally to red cell surface antigens. Although detection of polymorphism in
red cell surface proteins is attainable by other methods, for instance DNA sequences analysis,
unless defined by an antibody such variants cannot be titled blood groups. (Daniels,

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The ABO group system has four
main group types that blood groups are divided into: A, B, AB, and O. The genes
inherited from your parents determine this as blood type is inherited by
parents. One of two ABO genes are donated by each biological parent. The A and
B genes are dominant and the O gene is recessive. Antigens and antibodies found
in the blood identify an individual’s blood group. Antibodies are a protein found
within the plasma, they are part of the body’s natural defence mechanism
against invading substances such as germs. When foreign material enters the
body antibodies alert the immune system to destroy it. Whereas antigens are
protein molecules found on the surface of red blood cells. Red cells in the
blood that have type A antigens on the cell surface contain antibodies against type
B red cells in its serum. If type B blood is given to an individual with type A
blood, antibodies in the recipients blood will destroy the red cells of the
injected blood. Similarly, type A red cells will be destroyed by anti-A antibodies
in blood type B.

Rhesus (Rh)
blood grouping system splits blood groups in accordance to whether the Rh
antigen (Rh factor) is present or absent on the red blood cells cell membranes.
The most common Rh antigen is
termed RhD, this causes the most severe immune reaction and is the primary
determinant of the Rh trait. In clinical importance Rh is second to the
ABO blood groups (Flegel, 2007).  An individual that lacks the Rh
antigen could be in danger if Rh positive blood is given in transfusion. The
first time Rh incompatible blood is given there may not be effects, however the
response of the immune system is to produce anti Rh antibodies. After the          antibodies form, if Rh positive blood is given it can
cause agglutination as they will attack the foreign red blood cells. Resulting in haemolysis causes
serious illness or can be fatal. 

Different antigens and antibodies
are present in each group within the ABO systems, group O red blood cells have
no antigens therefore, can be used safely for any group types. Red blood cells
can have an additional antigen present, this is known as the RhD antigen, and
each blood group can be RhD positive or RhD negative. This is determined by the
presence of the antigen, if the antigen is present, it is positive and if it is
absent, it is negative.