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Ch.4 - Nucleic Acids and the RNA World
All textbooksFreeman 8th EditionCh.4 - Nucleic Acids and the RNA WorldProblem 5
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Chapter 4, Problem 5

What is responsible for the increased stability of DNA compared to RNA?

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Identify the structural differences between DNA and RNA: DNA has a deoxyribose sugar while RNA has a ribose sugar. DNA is double-stranded forming a helical structure, whereas RNA is typically single-stranded.
Understand the role of the sugar molecule: The presence of a hydroxyl group (-OH) on the ribose sugar in RNA makes it more reactive and less chemically stable than the deoxyribose sugar in DNA, which lacks this group at the 2' carbon.
Consider the impact of double-stranded structure: DNA's double-stranded structure with complementary base pairing provides additional stability through hydrogen bonds between the bases on opposite strands.
Examine the base composition: DNA contains thymine while RNA contains uracil, which lacks a methyl group present in thymine. This methyl group in thymine helps stabilize DNA by making it less prone to mutations.
Summarize the factors: The increased stability of DNA compared to RNA is due to the absence of the 2' hydroxyl group in its sugar, its double-stranded structure, and the presence of thymine instead of uracil.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chemical Structure of DNA and RNA

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) differ in their chemical structure, particularly in their sugar components. DNA contains deoxyribose, which lacks an oxygen atom at the 2' position, making it more stable than ribose in RNA. This structural difference contributes to DNA's overall stability, as the absence of the hydroxyl group in deoxyribose reduces susceptibility to hydrolysis.
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Double Helix Structure of DNA

DNA's double helix structure, formed by two complementary strands coiling around each other, provides significant stability. The hydrogen bonds between the base pairs (adenine-thymine and guanine-cytosine) and the stacking interactions between the bases help protect the genetic information. This structural arrangement makes DNA less prone to damage and degradation compared to the single-stranded RNA.
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Base Pairing and Repair Mechanisms

DNA's stability is further enhanced by its precise base pairing and efficient repair mechanisms. The complementary base pairing ensures accurate replication and reduces errors. Additionally, DNA has evolved sophisticated repair systems, such as nucleotide excision repair, which corrects damage caused by environmental factors, thereby maintaining its integrity over time, unlike RNA, which lacks such extensive repair capabilities.
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Textbook Question

What determines the primary structure of a DNA molecule? a. stem-and-loop configuration b. complementary base pairing c. deoxyribonucleotide sequence d. hydrophobic interactions and hydrogen bonding

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Textbook Question

Evaluate the following statements related to the synthesis of nucleic acids. Select True or False for each statement. T/F Ribonucleotides are added to the 3′ end of a DNA strand. T/F Polymerization of nucleic acids occurs by the formation of phosphodiester bonds. T/F Complementary pairing between sugars is required for copying nucleic acids. T/F Strands in a double helix are synthesized in an antiparallel orientation.

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Textbook Question

Single strands of nucleic acids are directional, meaning that there are two different ends. What functional groups define the two different ends of a strand?

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Textbook Question

If nucleotides from the DNA of a human were quantified and 30 percent of them contained the base adenine, what percentage of them would contain the base guanine? a. 20 percent b. 30 percent c. 40 percent d. 70 percent

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Textbook Question

What would be the sequence of the strand of DNA that is made from the following template: 5′-GATATCGAT-3′? (Your answer must be written 5'→3'.) How would the sequence be different if RNA were made from this DNA template?

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Textbook Question

According to the RNA world model, a ribozyme would replicate by creating a double-stranded RNA intermediate. Would you expect the intermediate to have the same catalytic activity as the original ribozyme? Justify your answer with an explanation.

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