Question

The enormous diversity exhibited by MHC molecules within a species originates from:

• A. Alternative splicing of MHC transcripts
• B. Somatic hypermutation in MHC genes
• C. Rearrangement of MHC gene segments
• D. Polymorphism in MHC genes

Hint:

Remember:
• MHC diversity \(\rightarrow\) Due to polymorphism
• Antibody diversity \(\rightarrow\) Due to gene rearrangement and somatic hypermutation \[ \text{MHC genes are among the most polymorphic genes known} \]

Answer 1

The Correct Option is D

Concept: Major Histocompatibility Complex (MHC) molecules are cell surface proteins involved in antigen presentation and immune recognition. MHC genes are among the most highly polymorphic genes in vertebrates. Polymorphism means the presence of multiple allelic forms of a gene within a population. This genetic variation produces enormous diversity in MHC molecules among individuals of the same species. Such diversity is important because it enables populations to respond to a wide variety of pathogens.

Step 1: Understanding the source of MHC diversity. The diversity of MHC molecules mainly arises due to: \[ \text{Large number of alleles in MHC genes} \] This phenomenon is called: \[ \boxed{\text{Polymorphism}} \] Different individuals inherit different combinations of MHC alleles, leading to extensive variation in antigen presentation capability.

Step 2: Eliminating the incorrect options.
• Option (A): Alternative splicing can generate protein variants but is not the major source of MHC diversity.
• Option (B): Somatic hypermutation occurs in immunoglobulin genes of B-cells, not in MHC genes.
• Option (C): Rearrangement of gene segments occurs in antibody and T-cell receptor genes, not in MHC genes. Therefore, the enormous diversity in MHC molecules originates from polymorphism in MHC genes. \[ \boxed{\text{MHC diversity} \Rightarrow \text{Gene polymorphism}} \]