In somatic recombination, the rearranges first. The region of the antibody molecule is generated via somatic recombination as it binds to the antigen and contains both a constant region and a variable region.

Correct Answer: A

Rationale: The heavy chain rearranges first, and the Fab region, which binds antigen, is generated via somatic recombination.

Correct Answer: C

Rationale: Deficiencies in either RAG-1 or RAG-2 can cause SCID due to impaired V(D)J recombination.

Correct Answer: D

Rationale: CD11a (LFA-1) is an adhesion molecule that stabilizes T cell interactions.

Correct Answer: D

Rationale: DRβ is the most polymorphic among MHC class II genes.

Correct Answer: D

Rationale: Pemphigus vulgaris is associated with HLA-DQ2.