This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basics of DNA, Subject name: Biochemistry
At physiologic pH, DNA is 
Select and explain. 
A. Positively charged, B. Negatively charged, C. Amphoteric, D. Uncharged
B: Negatively charged
Answer: B: Negatively charged 
Explanation: Nucleic acid carries negative charge at physiological pH Negative charge at physiologic pH is due to presence of phosphodiester linkages This propey is useful for the separation of DNA or RNA by electrophoresis. DNA will move towards the anode. Shoer DNA molecules will move faster than longer molecules in agarose gel electrophoresis.