Question

If a double-negative thymocyte has just completed a productive β-chain gene rearrangement, which of the following describes the immediate next step in the development of this thymocyte?

a. A pre-T-cell receptor is assembled.
b. Rearrangement of γ- and δ-chain genes commences.
c. Expression levels of RAG-1 and RAG-2 are elevated.
d. The linked δ-chain genes are eliminated.
e. This cell will inevitably differentiate into a committed γ:δ T cell.

Answer 1

The immediate next step in the development of a double-negative thymocyte that has completed a β-chain gene rearrangement is the expression of RAG-1 and RAG-2, causing the rearrangement of γ- and δ-chain genes.

Step-by-step explanation:

The immediate next step in the development of a double-negative thymocyte that has just completed a productive β-chain gene rearrangement is c. Expression levels of RAG-1 and RAG-2 are elevated. RAG-1 and RAG-2 are enzymes involved in V(D)J recombination, which is the process of rearranging gene segments to generate a diverse repertoire of T cell receptors (TCRs). After β-chain rearrangement, the expression levels of RAG-1 and RAG-2 are increased to initiate the rearrangement of γ- and δ-chain genes, which will then result in the generation of a functional γ:δ T cell receptor.