[Campbell Biology P.1009] A human produces more than 1 million different B cell antigen recep... | Practice Question

A human produces more than 1 million different B cell antigen receptors and 10 million different T cell antigen receptors, despite having only about 20,000 protein-coding genes. Which of the following is the primary mechanism described for generating this immense diversity, specifically for a light-chain gene?

  • A: The use of an extremely large number of distinct genes, each encoding a unique receptor.
  • B: Combinatorial joining of multiple gene segments (V, J, C) within a single gene locus.
  • C: Continuous spontaneous mutations occurring in all gene segments during lymphocyte development.
  • D: The unique folding patterns of each receptor protein, independent of its genetic sequence.

Explanation

The text explains that the vast diversity of antigen receptors is generated by combining a limited number of gene segments. Specifically for the light-chain gene, it states that a receptor light chain is encoded by variable V , joining J , and constant C segments, and these pieces can be combined in 200 different ways 40 V × 5 J × 1 C . This combinatorial joining is the primary mechanism.