Multiple Choice
RNA differs from DNA in that RNA uses which nitrogenous base in place of thymine?
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7. DNA and Chromosome Structure
RNA
Multiple Choice
In terms of chemical stability under alkaline conditions, why is DNA generally more stable than RNA?
A
DNA contains ribose while RNA contains deoxyribose, and ribose is less reactive than deoxyribose.
B
DNA uses uracil instead of thymine, and uracil makes the sugar-phosphate backbone more resistant to hydrolysis.
C
DNA is double-stranded whereas RNA is always single-stranded, and single-stranded nucleic acids cannot be chemically stable.
D
DNA lacks a ′ -hydroxyl group, so its backbone is less prone to base-catalyzed hydrolysis than RNA.
Verified step by step guidance1
Understand the chemical structure difference between DNA and RNA, focusing on the sugar component: DNA contains deoxyribose, while RNA contains ribose.
Recognize that ribose has a hydroxyl group (-OH) attached to the 2' carbon, whereas deoxyribose lacks this 2'-OH group (hence 'deoxy').
Learn that under alkaline conditions, the 2'-OH group in RNA can act as a nucleophile, attacking the adjacent phosphate group and causing cleavage of the phosphodiester bond, leading to backbone hydrolysis.
Note that DNA, lacking the 2'-OH group, does not have this internal nucleophile, making its sugar-phosphate backbone more chemically stable and less susceptible to base-catalyzed hydrolysis.
Conclude that the absence of the 2'-OH group in DNA is the key reason for its greater chemical stability under alkaline conditions compared to RNA.
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