Question

Select the correct statement from the following: (a) Surface antigen on RBC always induce autoimmune response. (b) Blood grouping (ABO) is an example of multiple allelism. (c) AB blood group is a universal recipient as well as donor. (d) 4 phenotype of blood group (ABO) are possible and 5 genotype of blood group (ABO) are possible.

Short answer

The correct statement is (b) Blood grouping (ABO) is an example of multiple allelism.

Step-by-step solution

Analyze options

Analyze each option in light of known biological facts: (a) Surface antigens on RBCs do not always induce autoimmune response, they may induce an immune response only in cases of mismatched blood transfusion. (c) The statement 'AB blood group is a universal recipient as well as donor' is incorrect because AB blood group is a universal recipient, but not a universal donor. (d) There are indeed 4 phenotypes of blood group (A, B, AB, O), but only 6 genotypes are possible (AA, AB, BB, BO, AO, OO), not 5.

Identify correct statement

The only remaining choice is (b), Blood grouping (ABO) is an example of multiple allelism. Multiple allelism refers to the situation when more than two alleles (Alternate versions of the same gene) determine a certain characteristic. In humans, the ABO blood group system is controlled by three alleles - A, B and O which results in four different blood groups - A, B, AB and O, which verifies the statement. Hence, the statement (b) is correct.

Key concepts

Multiple Allelism

In genetics, multiple allelism describes a situation where more than two alleles exist for a particular gene within a population. When it comes to the ABO blood group system, there are indeed three main alleles involved: A, B, and O.
Each person inherits two alleles, one from each parent, which determine their blood type. The combination of these alleles leads to the formation of different blood groups. For example:

• Alleles A and B are both dominant, while O is recessive.
• If both alleles are A, the person has blood group A.
• If both alleles are B, the person has blood group B.
• An AB combination results in blood group AB, showcasing co-dominance.
• Having two O alleles results in blood group O.

This variety is what makes the ABO system a prime example of multiple allelism, where more than two allele forms control a characteristic.

Blood Group Phenotypes

The term "phenotype" refers to the observable characteristics or traits of an organism. In the context of the ABO blood group system, the phenotypes are the actual blood groups that you can determine through a blood test. For the ABO system, there are four main phenotypes:

• Type A: Characterized by the presence of A antigens on the red blood cells.
• Type B: Characterized by the presence of B antigens.
• Type AB: Both A and B antigens are present; thus, this blood type is often called the universal recipient for plasma transfusions.
• Type O: Absence of both A and B antigens; known as the universal donor for red cell transfusions.

These phenotypes are directly influenced by the combinations of the alleles inherited by an individual.

Blood Group Genotypes

A "genotype" refers to the genetic makeup of an individual, specifically concerning the alleles inherited from the parents. Unlike the phenotypes, which only show the result, genotypes look at the specific allelic combinations. In the ABO system, the genotypes are combinations of the alleles A, B, and O. There are six possible genotypes:

• AA: Results in blood type A.
• AO: Also gives blood type A since A is dominant over O.
• BB: Results in blood type B.
• BO: Results in blood type B.
• AB: Gives blood type AB, showcasing the co-dominance of A and B alleles.
• OO: Results in blood type O, as O is recessive.

These genotypes explain why individuals with the same blood group phenotype may have different genetic makeups.

Immune Response in Blood Transfusion

The immune response during blood transfusion is an essential concept in medical biology. When receiving blood, it's crucial to ensure compatibility between the donor's and recipient's blood types.
An immune response can occur if blood is mismatched. Here's what happens in a typical case of immune response:

• If a recipient's immune system recognizes the donor's blood group antigens as foreign, it may trigger an immune reaction.
• This reaction involves the production of antibodies aimed at attacking the foreign blood cells, leading to potential complications.
• Type O blood, lacking both A and B antigens, is often considered a safe universal donor for red cell transfusions, but not plasma.
• Type AB individuals can receive red cells of any type because their plasma does not contain anti-A or anti-B antibodies.

Understanding these interactions helps prevent transfusion reactions and ensures safe blood transfusion practices.