Inheritance of blood groups

Introduction

The characters in the organisms are expressed by a pair of alleles known as gene. A allele can be dominant or recessive. The dominant allele expresses itself irrespective of the other gene present,while the recessive allele is only expressed in the presence of the second recessive allele.

Definition

The inheritance of blood groups means that a baby inherits blood groups from both the parents like other qualities, for example, height, eye colour, etc.   

 Inheritance of blood groups classification

The  Austrian Scientist  Karl Lnasteiner found the ABO blood group system in 1900. He did experiments on different blood types by mixing them. He noted that the plasma from certain blood types created groups or generated agglutinates due to the scarcity of molecules on red blood cells and resulted in antibodies to overthrow that molecule. He then remarked on agglutination and divided their blood types into four categories.

The blood grouping system is crucial in blood transfusion. Our immune system acknowledges another blood type as unfamiliar and attacks it if inducted into the body resulting in a transfusion reaction. Any improper match with the Rh and ABO blood types result in the most severe and life-threatening transfusion reactions. Thus, it is recommended to have a blood group checked before blood transfusion.

Gene I controlled the inheritance of blood groups. Gene I has three types of alleles: IA ,IB and i. Every person inherits a pair of alleles from their parents.  And both IA and IB are  dominant over  i.

Blood group

Genotype

AB

I A I B

A

I A I A

A

IA i

B

IBIB

O

i i

B

IBi

ABO blood group system

The ABO blood group system comprises four kinds of blood groups – AB, A, B and O. It is primarily based on the antibodies and antigens on RBCs and in the plasma. Both antibodies and antigens are protein molecules in which antibodies are present in the plasma, entangled in protecting mechanisms, and antigens exist on the surface of Red Blood Cells.

The source of ABO categorising is of 2 antigens- Antigen B and Antigen A. The ABO grouping system is categorised into four categories based on the existence or absence of antigens on BRC’s surface and antibodies in the plasma.

  • Group A – comprises antibody B and antigen A.
  • Group B – comprises antibody A and antigen B
  • Group AB –comprises both antigen B and Antigen A, and neither antibody A nor antibody B.
  • Group O – comprises neither antigen B and Antigen A and both  antibodies A and B present.

The ABO group system is crucial during a blood transfusion, or blood donation as mismatching of blood groups can direct to clumping of red blood cells causing  various illnesses. It is significant for the blood cells to match while transfusing, which is essential for donor-recipient compatibility. Let us look at an example for blood transfusion, an individual of blood group A can collect blood either from group O or A as there are no antibodies for O or A in blood group A.

People of blood group O are called universal donors, whereas people of blood group AB are called universal recipients.

Rh Blood Group System

The other essential blood group system is the Rh system of the; blood group. About 2/3 of the population includes the 3rd antigen on the surface of the RBCs, which is named as Rh antigen; another name is Rh factor. This system concludes whether the blood group is +ve or -ve. If the Rh factor exists, then a person is Rh+ve or rhesus positive, and if an Rh factor is not present, then the person is Rh-ve or rhesus negative as they generate Rh antibodies.  This means a person can be one of these eight blood groups:

  1. A+ or A RhD +ve
  2. B+ or B RhD +ve
  3. O+ or O RhD +ve
  4. AB+ or AB RhD +ve
  5. A- or A RhD -ve
  6. B- or B RhD -ve
  7. O- or O RhD -ve
  8. AB- or AB RhD -ve

Thus, compatibility between donor and recipient is also essential in this circumstance.

Conclusion

In this article, we have discussed the Inheritance of blood groups, their definition and classification. Human beings inherit blood groups from our parents, similar to other qualities. And blood grouping is essential in blood donation and blood transfusion as mismatched blood groups can cause transfusion reactions. The two most significant group systems evaluated during the blood transfusion are the ABO blood grouping system and the Rh blood group system. 

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