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
[{'content': 'If a 4 nucleotide sequence code for an amino acid instead of 3 then theoretically how many unique amino acids could be coded by such a system? \nSelect and explain. \nA. 16, B. 64, C. 128, D. 256', 'role': 'user'}, {'content': 'Answer: D \nExplanation: There are four types of nucleotides (A, T, G, C).\nNormally the codons are made up of 3 nucleotides. Thus there are 43\xa0= 64 possible codon combinations.\nIf the codons are made up of 4 nucleotides, then there would be 44\xa0= 256 possible codon combinations.\nIf the codons are made up of 2 nucleotides, there would be 42\xa0= 16 possible codon combinations.', 'role': 'assistant'}]