Question

Each functional immunoglobulin has two heavy chains and two light chains. If an immunoglobulin is unable to bind to antigen, what is it lacking?

• A. Variable region of heavy chain
• B. Variable region of light chain
• C. Constant region of light chain
• D. Variable region of both heavy and light chain

Answer 1

The correct option is D Variable region of both heavy and light chain

This is the structure of a typical antibody.
The variable region of both the heavy and the light chain is the portion which identifies and attaches to an antigen. This is called as the antigen binding site. Therefore a functional immunoglobulin lacking this antigen binding site will be unable to bind to an antigen.