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
If there are 4 nucleotides instead of 3 in codon, how many amino acids may be formed ? 
Select and explain. 
A. 16, B. 21, C. 256, D. 64
C: 256
Answer: C: 256 
Explanation: Formula for calculating no. of codons = (4)n

n = no. of nucleotides that constitute codon.
e.g. if n = 2; no. of codons = (4)2 = 16
if n = 3; no. of codons = (4)3 = 64
if n = 4; no. of codons = (4)4 = 256
so on