Ch.4 - Nucleic Acids and the RNA World

Freeman - Biological Science 8th Edition

Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook

Freeman 8th Edition

Ch.4 - Nucleic Acids and the RNA World

Problem 8

Chapter 4, Problem 8

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.

Verified step by step guidance

Understand the RNA world model: The RNA world model suggests that early life forms may have used RNA both to store genetic information and to catalyze chemical reactions, with ribozymes (RNA molecules with enzymatic activity) playing a crucial role.

Recognize the structure of ribozymes: Ribozymes are single-stranded RNA molecules that fold into specific three-dimensional shapes, allowing them to catalyze specific chemical reactions.

Consider the nature of the double-stranded RNA intermediate: During replication, a complementary RNA strand pairs with the original ribozyme, forming a double-stranded RNA. This double-stranded structure is likely more rigid and lacks the flexibility of the single-stranded form.

Analyze the impact of double-stranded formation on catalytic activity: The specific three-dimensional structure required for catalytic activity in ribozymes is generally disrupted when the RNA forms a double-stranded complex. This structural change can inhibit the ribozyme's enzymatic function.

Conclude the catalytic activity comparison: Based on the structural changes upon forming a double-stranded RNA, it is unlikely that the intermediate would have the same catalytic activity as the original single-stranded ribozyme.

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Key Concepts

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

RNA World Hypothesis

The RNA World Hypothesis posits that early life forms may have relied solely on RNA for both genetic information storage and catalysis. This theory suggests that RNA molecules, capable of self-replication and catalyzing chemical reactions, were precursors to current life forms, which utilize DNA and proteins. Understanding this concept is crucial for analyzing the role of ribozymes in early biological systems.

Ribozymes

Ribozymes are RNA molecules that possess catalytic properties, enabling them to facilitate biochemical reactions, similar to protein enzymes. They can perform various functions, including RNA splicing and peptide bond formation. The catalytic activity of ribozymes is essential for understanding how RNA could have played a role in early life and how it might replicate through intermediates.

Catalytic Activity and Structure

The catalytic activity of a ribozyme is closely linked to its three-dimensional structure, which determines its ability to bind substrates and facilitate reactions. When a ribozyme creates a double-stranded RNA intermediate, the structural changes may affect its catalytic properties. Therefore, understanding how structural differences influence activity is key to answering whether the intermediate retains the same catalytic function as the original ribozyme.

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Related Practice

Textbook Question

Make a concept map that relates DNA's primary structure to its secondary structure. Your diagram should include deoxyribonucleotides, base-stacking interactions, purines, pyrimidines, phosphodiester linkages, DNA's primary structure, DNA's secondary structure, complementary base pairing, and antiparallel double helix.

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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

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

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