On the surface of red blood cells, there is a specific marker for allele A and B code. It is called antigens Allele O by default means absence of antigen. The antibodies produce by human immune system will against antigens that are located on red blood cells. So, a person with type A blood will have antibodies to antigen B but not to antigen A, as A is the self-antigen and is recognized as such by the immune system. A person with type B blood will have antibodies to antigen A, and a person with type AB blood will not have either of the antibodies. A person with type O has both anti-A and anti-B antibodies but no A or B antigens. Thus, since type O blood has anti-A and anti-B antibodies, a person with type O blood can only receive blood of the same type. Conversely, type AB blood cannot be given to any other blood type except AB, as it has both the antigens.
Genes that code for blood type alleles are located on chromosome 9. A child inherits one of the three alleles A, B and O from each parent. The possibilities for blood type in the child depending on the blood types of the parents are:
The genes that code for blood type alleles are somehow related to the function of the genes, which code for the blood clotting factors. It is because some blood types have been linked to increased susceptibility to certain diseases. For example, cancers of the gastrointestinal tract are more associated with type A blood, but not type O blood. Some types of cardiovascular disease, specifically myocardial infarction and thromboembolism, have been found with increased frequency in persons with type A and type AB blood.
With the development and widespread use of genetic analysis techniques, it became obvious that there may be more than four blood types in humans. Some data suggests that different persons may have genetically determined underexpression or overexpression of the enzymes, which convert the precursors of the A and B antigens into the functional antigens. It is also possible that evolution of human blood types continues, and the so-called blood subtypes are the new blood types in the process of formation.
From:
Name: Tze Kwong Tay
Student id: 41925834
References:
[1] "Relationship between Lewis phenotype, clotting factors and other cardio-vascular risk factors in young adults" - Green D; Journal of Laboratory Clinical Medicine,1995;125(3):334-9.
[2] "Cytogenetic patterns following bone marrow transplantation for chronic granulocytic leukemia" - da Silva MA; Cancer Genetics,1988;36(1):35-44.
[3] "Uncertainty in identification of blood group A subtypes by agglutination test" - Joshida; Human Heredity,1985;35(1):1-6.
[4] "Problems in paternity testing. Subtypes of AB" - Perkins UA; American Journal of Clinical Pathology,1980;73(2):263-6.
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