Question

Arrange the following in the order of the production of ABO blood group system antigen.
• [A.] Production of H substance
• [B.] Production of glycosyltransferase enzyme
• [C.] Addition of an extra group
• [D.] Formation of A and B antigen
Choose the correct answer from the options given below :

• A. A-B-C-D
• B. B-C-A-D
• C. C-A-B-D
• D. A-C-B-D

Hint:

H substance is the precursor for ABO blood groups. Glycosyltransferase enzymes modify it by adding specific sugars to form A and B antigens.

Answer 1

The Correct Option is A

Concept: The ABO blood group system is determined by the presence or absence of specific antigens on the surface of red blood cells. The production of ABO antigens occurs through:
• Formation of precursor substances,
• Enzymatic action,
• Addition of sugar molecules,
• Final antigen expression. The H substance acts as the precursor for both A and B antigens.

Step 1: Production of H substance. The very first stage involves: \[ Formation of H substance \] The H antigen serves as:
• The basic precursor molecule,
• The foundation upon which A and B antigens are formed. Without H substance:
• A antigen cannot form,
• B antigen cannot form. Thus: \[ A = \text{First step} \]

Step 2: Production of glycosyltransferase enzyme. The ABO genes then produce: \[ Specific glycosyltransferase enzymes \] These enzymes are responsible for:
• Transferring sugar molecules,
• Modifying the H substance,
• Creating antigen specificity. Hence: \[ B = \text{Second step} \]

Step 3: Addition of extra group. The glycosyltransferase enzyme adds:
• N-acetylgalactosamine for A antigen,
• Galactose for B antigen. This process is described as: \[ Addition of an extra group \] Thus: \[ C = \text{Third step} \]

Step 4: Formation of A and B antigens. After the additional sugar groups are attached: \[ A and B antigens are finally formed \] Therefore: \[ D = \text{Final step} \]

Step 5: Determining the correct sequence. The correct biological order becomes: \[ A \rightarrow B \rightarrow C \rightarrow D \] Thus: \[ \boxed{\text{(A) A-B-C-D}} \]