Blood Groups
Definition:
Blood groups are inherited features. They are carried from parents to their offspring via genes/chromosomes.
At least 30 ordinarily occurring antigens and hundreds of other rare antigens are found in human blood. These are present on the surface of cell membranes. Each can cause an antigen-antibody reaction. Two specific groups of antigens are more probably to cause blood transfusion reactions.
Types:
OAB or ABO blood groups (classical blood groups)
ABO blood groups are further classified in to:
O = 47%
A = 41%
B = 9%
AB = 3%
Rh blood group system
- (a) Rh +ve
- (B) Rh -ve
Other blood group system
L, MNS, KELI, Lewis, Kidd, Duffy, etc
Antigen:
These are foreign substances that can elicit an immunological response; antigens are present on the surface membranes of RBCs, in saliva, the cornea platelets, WBCs, and epidermal cells.
Agglutinogen:
These are present on the surface membrane of RBCs which can cause agglutination on combining with corresponding antibodies.
Antibodies:
These are humeral substances generated in response to antigens.
Agglutinins:
These are antibodies (immunoglobulins) that cause agglutination upon grooming with corresponding agglutinogens.
Type:
- Anti -A agglutinin
- Anti -B agglutinin
Blood types showing antigen and antibody composition of A, B, O blood groups:
Figure.....
Inheritance of ABO groups
Two genes, one on each of the two paired chromosomes, determine the ABO Blood groups. There are allelomorphic genes that can be any one of the three different types. But only one type on each chromosome.
Genotype:
This is a combination of different genes.
Phenotype:
This is the way in which the individual gene expresses itself.
1st character 2nd character Genotype Blood group (phenotype)
A A AA A
A B AB AB
A O AO A
B B BB B
B O BB B
O O OO O
Genotype "OO" produces no agglutinogen. Genotype OA or AA creates agglutinogen A, genotype OB or BB creates agglutinogen B, genotype AB can produce agglutinogen A and B, this genotype matching can help in identifying the blood group of future offspring.
Father-Mother
AAB Phenotyer (Blood group)
Figure...
A AABA BPhenotype (Blood group)
Result
Blood Group A: 50% Chances
Blood Group AB: 50% Chances
Inheritance of Rh blood groups
Rh-System/Rh Factor:
Definition:
Rh factors are antigens present on the surface of RBCs which cause agglutination on mixing blood with anti-Rh D serum.
The Rh blood group is due to the presence of gene "D" which is dominant over its allelomorphic gene "d"which is recessive.
In Rh blood groups, the following genotype and phenotype are possible.
1st character 2nd character Genotype Phenotype (blood group)
D D DD Rh+ve
D D Dd Rh+ve
D D dd Rh-ve
The possible blood group of the children of a couple with genotype Dd and dd.
Father-Mother
Figure......
Phenotype:
Rh+ve: 50% chances
Rh-ve 50% chances
Rh. factor transfusion reaction:
When Rh+ve blood is transfused into Rh-ve persons, anti-Rh-D antibodies do not develop during the first exposure. On the second exposure of Rh+ve blood to an Rh-ve person, the individual will produce sufficient anti-D antibodies which will cause a reaction known as a delayed transfusion reaction. This type of reaction occurs in the condition of erythroblastosis fetalis.
Figure.......
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