This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Idiotypic class of antibody is determined by - 
Select and explain. 
A. Fc region, B. Hinge region, C. Carboxy end, D. Amino end
D: Amino end
Answer: D: Amino end 
Explanation: An idiotype is a shared characteristic between a group of immunoglobulin or T cell receptor (TCR) molecules based upon the antigen binding specificity and therefore the structure of their variable region. The variable region of antigen receptors of T cells (TCRs) and B cells (immunoglobulins) contain complementarity-determining regions (CDRs) with unique amino acid sequences Ref: www.mayoclinic.com