Question

why DNA is negatively charged? ​

Answer 1

$\huge\underline\green{\sf Answer}$

★ Phosphate backbond of DNA is negatively charged due to bonds created between phosphorous atoms and the oxygen atoms

★ Each phosphate group contains one negatively charged oxygen atom, therefore the entire strand of DNA is negatively charged due to repeated phosphate groups.

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Answer 2

We know that non-metals are of negative charge or they are anion. DNA is a composition of oxygen and phosphorous and both the elements belongs to the phosphate group. And to be stable they gains electrons as a result the entire constituents of DNA is negative so, DNA can also be considered as negative. Moreover the DNA compounds bind nitrogen bases with it which is too non-metal and with valence electron 5 so, to complete its octate and to be stable, it too gains electron and as a result it too forms anion.