RNA can be hydrolyzed by dilute alkali but not DNA. explain why?

Answer 1

in short, RNA has a free 2' hydroxyl group DNA doesnt.

DNA has 2-deoxyribose sugar on its backbone [hydrogen instead of hydroxyl group on 2' position]. It used its 3' hydroxyl to link two molecule of nucleotides together, so there's no free hydroxyl group hanging around. RNA has a free 2' hydroxyl group; it can be used as a nucleophile, although it's fairly weak, to attack the phosphorus atom in the phosphodiester bond and therefore break the bond, in another word, RNA hydrolyzes itself. a basic condition might help the hydrolysis process by making RNA itself a better nucleophile.

that's why RNA is less stable than DNA and the cell can target specifically the RNA and destory them while keep all DNA molecules safe. Another way to think about this is, to remove 2' hydroxyl group on ribose sugar takes energy, if it is not essential to its survival, the cell wont be doing it.

Answer 2

DNA CONTAINS 2-DEOXYRIBOSE BUT RNA DOES NOT