Final answer:
The statement that all antigen-binding sites are concave is false, as these sites can adopt various shapes to specifically match antigens. Antibody diversity is due to the diversity of the variable region rather than each antibody being encoded by a unique gene.
Step-by-step explanation:
The statement 'All antigen-binding sites are concave in shape' is false. While many antibody antigen-binding sites are indeed concave, they can also adopt other shapes that complement the shape of their specific antigen. This complementarity between the antigen and the antibody's antigen-binding site is crucial for the specificity of an immune response.
The vast diversity of antibodies and their specific antigen-binding sites is facilitated by the diversity of the variable region of antibodies. Given the human genome contains fewer genes than the number of different antibodies it can produce, the diversity is achieved through a combination of gene segment rearrangements, somatic hypermutation, and class switching.