This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which is the smallest fundamental unit coding for protein synthesis 
Select and explain. 
A. Cistron, B. Operon, C. Replican, D. Anticodon
A: Cistron
Answer: A: Cistron 
Explanation: Cistron is the smallest unit of genetic expression that codes for one polypeptide chain.