Final answer:
During TCRα chain gene rearrangement, a variable (Vα) and a joining (Jα) gene segment are combined while the diversity (D) gene segment is absent. This genetic process is key for the creation of diverse T-cell receptors essential for immune response.
Step-by-step explanation:
The chromosomal T-cell receptor alpha (TCRα) chain gene rearrangement involves the combination of variable (V) and joining (J) segments without the diversity (D) segment. During this genetic rearrangement, which is crucial for the development of TCRs, one variable (Vα) gene segment is paired with one joining (Jα) gene segment to code for the variable region of the α chain. On the other hand, the TCRβ chain involves the recombination of variable (V), diversity (D), and joining (J) gene segments. As a result, a chromosome on which T-cell receptor alpha chain gene rearrangement has occurred lacks the diversity (D) gene segment. The constant (C) region remains unchanged, and there is no involvement of the TCR beta chain (β) gene segments in the rearrangement of the α chain gene.