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
What is the codon for selenocysteine? 
Select and explain. 
A. UAG, B. UGA, C. UAA, D. GUA
B: UGA
Answer: B: UGA 
Explanation: Ans: B. UGA(Ref Harper 30/e p18, 286)Selenocysteine:Commonly termed "21st amino acid".Present in biological proteins.Not coded directly in genetic code.Instead encoded by a UGA codon.UGA codon - Normally a stop codon.This mechanism called as|"translational recoding".