Q."DNA molecule is more stable genetic material than RNA." Explain, why ?
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Start your 14-day free trial to unlock the full solution →DNA's deoxyribose sugar (no reactive 2'-OH), its double-helical structure, and its use of thymine instead of uracil together make it chemically far more stable and durable than the single-stranded, ribose-containing RNA — which is why DNA, not RNA, serves as the primary hereditary material in most organisms.
The greater chemical stability of DNA compared to RNA as a genetic material can be explained by several structural differences:
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Absence of the 2'-OH group — DNA contains deoxyribose sugar, which lacks a hydroxyl (-OH) group at the 2' carbon position (it has only -H there), whereas RNA contains ribose sugar with a reactive -OH group at the 2' position. This 2'-OH group makes the phosphodiester backbone of RNA chemically far more reactive and susceptible to hydrolysis (it can attack the adjacent phosphodiester bond under alkaline conditions), so RNA degrades much more readily than DNA. The absence of this group makes DNA chemically more inert and stable.
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Thymine instead of uracil — DNA uses the base thymine (5-methyluracil) in place of the uracil found in RNA. Cytosine in DNA can spontaneously undergo deamination to form uracil as a mutational error. Because DNA's "normal" pyrimidine is thymine and not uracil, any uracil found in DNA is immediately recognisable as a damaged/mistaken base and can be excised and corrected by DNA repair enzymes (base excision repair). If DNA normally used uracil (as RNA does), such deamination errors would go undetected. This gives DNA a built-in error-correction advantage that keeps the genetic information stable over generations.
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Double-helical, double-stranded structure — DNA exists as a double helix of two complementary, antiparallel strands held together by hydrogen bonds, whereas RNA is normally single-stranded. The double-stranded structure of DNA protects the genetic information — a break or lesion in one strand can be repaired using the complementary (undamaged) strand as a template, which is generally not possible for single-stranded RNA.
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