This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure of DNA, Subject name: Biochemistry
At the physiological pH the DNA molecules are 
Select and explain. 
A. Positively charged, B. Negatively charged, C. Neutral, D. Amphipathic
B: Negatively charged
Answer: B: Negatively charged 
Explanation: Ans. is 'b' i.e. Negatively charged DNA molecules are negatively charged, this is evident as it is stained by a cationic (positively charged) dye.Read the following lines for Ronald Hoffman Hematology:"Anionic cellular elements (nuclear DNA) reacts with cationic dye (Methylene blue)"