Question

DNA fragments are 

(a) positively charged 

(b) negatively charged 

(c) neutral 

(d) either positively or negatively charged depending on their size

Answer 1

Correct option is (b) negatively charged

DNA fragments are negatively charged molecules. The reason why DNA is negatively charged is the phosphate (\(PO^{2-}_4\)) group that constitutes every nucleotide. 

During the formation of phosphodiester bond, nucleotides retain one of the two negative charge, while the other is lost to form ester bond to new pentose.