Question

Why is DNA more stable than RNA? Reinforce your discussion with chemical structures.

Answer 1

Answer- the structure if DNA and RNA both have a ssugar , base and phosphate backbone. The difference is in the sugar, in DNA ,the sugar is a pentose or 5 carbon sugar called deoxyribose sugar while in RNA ,its a pentose as well but it's ribose sugar which has an additional OH group on 2nd carbon . Hydroxyl groups are reactive by nature and can act as a nucleophile which can hydrolyse the phosphate backbone ,so RNA becomes susceptible to hydrolysis.

Another difference in chemical structure is that DNA contains thymine while RNA has uracil . Thymine confers additional stability to photomutation and also undergoes methylation which helps in detection if mutations to repair.

Also DNA is a double stranded helix structure but RNA is single stranded so it can form secondary or tertiary structures ,it has free bases which can react with foreign electrophiles. In DNA two strands are bound by multipe double and triple bonds , so no free reactive bases . All are bound by complementary base pairing.

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