Blood group detection in Human beings

Hello everyone,

How many you know how to identify blood group?

Through this article I am going to share with you the basics of blood grouping. As you all might be knowing humans have four types of blood grouping i.e A, B, AB, and O. There is also a Rh factor determining positive or negative.

Concept of allelism

Genes are the pillars of our life. The things like how we are and how we behave are totally dependent upon the gene expression. Alleles are the pairs of genes occupying a specific spot called on a chromosome. Allelism refers to any of the several forms of a gene. These genetic variations arise usually through mutation and therefore are responsible for hereditary variations. Typically, there are only two alleles for a gene in a diploid organism. When there is a gene existing in more than two allelic forms this condition is referred to as multiple allelism.

Dominant and recessive phenotype:

The phenotype represents the physical structure of the body. There are two types dominant and recessive. As we can understand from the word dominant means which is leading. Same happens with the dominant allele.For example, if both the parents are tall, there are ample chances of the child being tall. We can know from this example that some traits are inherited. Even blood group is inherited. There will be permutation and combination which leads to child’s blood group.

Multiple allelism:

It is the case when two or more forms of allele are present.  In the inheritance of ABO blood group in humans, gene I  exists in three allelic forms: IA, IB, and IO. IA and IB are codominant. IO is a recessive allele and does not produce antigen. It should be noted though that even if there are more than two alleles present in the population, the individual comprising the population would possess only two such alleles. Thus, in the case of ABO blood group system, the inheritance of IA and IB alleles results in having a blood type AB.


  • The ABO system: There are 4 main blood groups defined by the ABO system:
  • blood group A – has A antigens on the red blood cells with anti-B antibodies in the plasma
  • blood group B – has B antigens with anti-A antibodies in the plasma
  • blood group O – has no antigens, but both anti-A and anti-B antibodies in the plasma
  • blood group AB – has both A and B antigens, but no antibodies
  • Blood group O is the most common blood group. 

How blood group detection is done in labs??

Many reputed industries have come up with chemicals and reagents which help in easy detection of blood group. There will be 3 bottles labelled as Anti-A, Anti-B and Anti-D. Anti-D is used to detect Rh factor i.e, positive or negative. The lab technician prepares a slide with the 3 reagents, each one drop. Later they take the blood sample and put some drops on the reagents and mix the three drops individually with three different sticks. The analysis would be, if the clump formation is seen in Anti-A drop then person is of A blood type, if clumps are seen in Anti-D then it shows positive. So becomes A positive. If the Anti-A and Anti-B doesn’t show clump formation then it is O blood group.

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