Final answer:
The constant regions of BCR and TCR are the C regions, which determine the biological properties of antibodies apart from antigen binding and provide consistency across antibodies of the same isotype.
Step-by-step explanation:
The constant regions of B cell receptors (BCR) and T cell receptors (TCR) are the C regions. These regions are coded by constant (C) DNA regions that do not vary significantly between different immunoglobulin or T cell receptors. Unlike the variable (V), diversity (D), and joining (J) regions, which are involved in creating the diverse antigen-binding sites needed for immune recognition, the constant regions largely determine the effector function and biological properties of the antibodies produced by B cells after activation.
The constant domains are consistent across all antibodies of the same isotype, which means they are not involved in binding antigen. However, they are crucial for the interaction with other components of the immune system.