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Ch. 17 - Transcription, RNA Processing, and Translation
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
All textbooksFreeman 8th EditionCh. 17 - Transcription, RNA Processing, and TranslationProblem 5
Chapter 17, Problem 5

RNases and proteases are enzymes that destroy RNAs and proteins, respectively. Which of the following enzymes, if added to a spliceosome, would be predicted to prevent recognition of pre-mRNA regions critical for splicing?
a. An RNase specific for tRNAs
b. An RNase specific for snRNAs
c. A protease specific for initiation factors
d. A protease specific for a release factor

Verified step by step guidance
1
Understand the role of the spliceosome: The spliceosome is a complex of proteins and small nuclear RNAs (snRNAs) that facilitates the removal of introns from pre-mRNA during RNA splicing. Both proteins and snRNAs are critical for its function.
Analyze the options: Each enzyme listed targets specific molecules. RNases degrade RNA, while proteases degrade proteins. Determine which molecule is essential for the spliceosome's ability to recognize pre-mRNA regions critical for splicing.
Focus on snRNAs: snRNAs are integral components of the spliceosome. They directly bind to pre-mRNA and help recognize splicing sites. If an RNase specific for snRNAs is added, it would degrade these snRNAs, preventing the spliceosome from functioning properly.
Evaluate the role of proteins: Proteins in the spliceosome assist in structural stability and enzymatic activity. However, initiation factors and release factors are not directly involved in splicing. A protease targeting these proteins would not affect the spliceosome's ability to recognize pre-mRNA regions.
Conclude the prediction: Based on the analysis, the enzyme that would prevent recognition of pre-mRNA regions critical for splicing is an RNase specific for snRNAs, as it would degrade the snRNAs essential for spliceosome function.

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Key Concepts

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

Spliceosome Function

The spliceosome is a complex of RNA and protein that facilitates the removal of introns from pre-mRNA. It recognizes specific sequences at the intron-exon boundaries, ensuring that only the coding regions are joined together to form mature mRNA. Understanding the spliceosome's role is crucial for determining how its function can be disrupted by various enzymes.
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Functional Groups

Types of RNases

RNases are enzymes that degrade RNA molecules. Different RNases target specific types of RNA, such as tRNA or snRNA. In the context of splicing, snRNAs are integral components of the spliceosome, and their degradation by an RNase would hinder the spliceosome's ability to recognize and process pre-mRNA correctly.
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Types of Phosphorylation

Proteases and Their Specificity

Proteases are enzymes that break down proteins by cleaving peptide bonds. Their specificity determines which proteins are affected. In the context of the question, understanding the role of initiation factors and release factors is important, as their degradation may not directly impact the spliceosome's ability to recognize pre-mRNA, unlike the degradation of snRNAs.
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Receptor Specificity
Related Practice
Textbook Question

Where is the start codon located?

a. At the start (5′ end) of the mRNA

b. In the DNA just upstream of where transcription starts

c. At the downstream end of the 5′ untranslated region (UTR)

d. At the upstream end of the 3′ untranslated region (UTR)

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Textbook Question

Splicing begins:

a. As transcription occurs.

b. After transcription is complete.

c. As translation occurs.

d. After translation is complete.

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Textbook Question

Compared with mRNAs that have a cap and tail, predict what will be observed if a eukaryotic mRNA lacked a cap and poly(A) tail.

a. The primary transcript would not be processed properly.

b. Translation would occur inefficiently.

c. Enzymes on the ribosome would add a cap and poly(A) tail.

d. tRNAs would become more resistant to degradation.

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Textbook Question

For each of these statements about the genetic code, select True or False.

a. T/F Wobble pairing accounts for the redundancy of the genetic code.

b. T/F There are 64 different tRNAs that read the 64 possible codons.

c. T/F All possible codons are used, but not all codons specify an amino acid.

d. T/F Some codons are recognized by proteins, not by tRNAs.

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Textbook Question

In a particular bacterial species, temperature-sensitive conditional mutations cause expression of a wild-type phenotype at one growth temperature and a mutant phenotype at another—typically higher—temperature. Imagine that when a bacterial cell carrying such a mutation is shifted from low to high growth temperatures, RNA polymerases in the process of elongation complete transcription normally, but no new transcripts can be started. The mutation in this strain most likely affects:

a. The terminator sequence

b. The start codon

c. Sigma

d. One of the polypeptides of the core RNA polymerase

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Textbook Question

In what ways are a promoter and a start codon similar? In what ways are they different?

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