Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Bovine serum albumin (BSA) is not immunogenic when injected into cow but is strongly immunogenic when injected in rabbit.
Reason R: The greater the phylogenetic distance between two species, the less the structural disparity between them.

• A. Both A and R are correct and R is the correct explation of A
• B. Both A and R are correct but R is NOT the correct explation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Immunogenicity depends directly on "Foreignness":
Greater Phylogenetic Distance = GREATER Structural Disparity = Higher Immunogenicity.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question tests concepts regarding antigenicity, foreignness, immunogenicity, and the relationship between evolutiory phylogenetic distance and protein structural divergence.

Step 2: Key Formula or Approach:
For a molecule to act as a potent immunogen, it must be recognized as "non-self" (foreign) by the recipient immune system.
Greater evolutiory (phylogenetic) distance between species causes greater cumulative sequence and structural divergence in homologous proteins.

Step 3: Detailed Explation:

• Alysis of Assertion A: Bovine Serum Albumin (BSA) is a self-protein in cows; injecting BSA into a cow does not elicit an immune response due to self-tolerance. However, when injected into a rabbit (a phylogenetically distant species), the rabbit immune system recognizes BSA as foreign, mounting a strong primary antibody response. Thus, Assertion A is correct.

• Alysis of Reason R: Evolutiory divergence dictates that the *greater* the phylogenetic distance between two species, the *greater* (not less) the structural disparity and sequence differences between their homologous proteins. Therefore, the claim in Reason R is factually incorrect.

Step 4: Fil Answer:
Assertion A is correct, but Reason R is incorrect.