Final answer:
The statement about an individual BCR having different L-chain isotypes on each arm is false. BCRs have two identical light chains that form a symmetric Y-shape, ensuring the same antigen specificity on both arms.
Step-by-step explanation:
An individual BCR (B-cell receptor) having one L-chain isotype on the left arm and another L-chain isotype on the right arm is false. B-cell receptors are composed of two identical heavy chains and two identical light chains, creating a symmetrical Y-shaped structure where both arms of the Y have identical antigen-binding specificity.
In the development of BCRs, each B-cell undergoes genetic rearrangement, which leads to the expression of a unique specificity for antigen binding. This process creates diversity but maintains the identical nature of the light chains within a given BCR. The BCRs on the surface of each B-cell are all identical to each other, which means that each receptor on a single B-cell binds the same specific antigen, thus refuting the idea of having different L-chain isotypes on each arm of one receptor.