This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Which of the following special amino acid is not formed by post-translational modification? \nSelect and explain. \nA. Triodothyronine, B. Hydroxyproline, C. Hydroxylysine, D. Selenocysteine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D. SelenocysteineSelenocysteine is formed by cotranslational modification. All others are derived amino acids. Derived amino acids are formed by post-translational modification.', 'role': 'assistant'}]