This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Translation, Subject name: Biochemistry
How many base pairs are encoded by a prokaryotic polypeptide of 250 amino acids? 
Select and explain. 
A. 250 bp, B. 500 bp, C. 750 bp, D. 1000 bp
C: 750 bp
Answer: C: 750 bp 
Explanation: A prokaryotic DNA does not contain any introns and the base sequence is exactly collinear with the amino acid sequence of proteins. Each amino acid is represented by a 3 base codon, therefore 250 amino acid protein will require 750 base pairs (250 x 3 = 750).