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Ch. 8 - Molecular Biology of Transcription and RNA Processing
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 8 - Molecular Biology of Transcription and RNA ProcessingProblem 28a
Chapter 8, Problem 28a

Assume that a mutation affects the gene for each of the following eukaryotic RNA polymerases. Match each mutation with the possible effects from the list provided. More than one effect is possible for each mutation.
Table listing RNA polymerase mutations and their potential effects, with spaces for user input.
Pre-mRNA does not have introns removed.

Verified step by step guidance
1
Understand the role of each RNA polymerase in eukaryotic transcription: RNA polymerase I synthesizes rRNA (ribosomal RNA), RNA polymerase II synthesizes pre-mRNA (precursor messenger RNA) and some snRNA (small nuclear RNA), and RNA polymerase III synthesizes tRNA (transfer RNA) and 5S rRNA.
Analyze the mutation effects: If RNA polymerase I is mutated, rRNA synthesis will be disrupted, affecting ribosome assembly and protein synthesis. If RNA polymerase II is mutated, pre-mRNA synthesis will be impaired, leading to issues with mRNA production and potentially affecting snRNA synthesis. If RNA polymerase III is mutated, tRNA and 5S rRNA synthesis will be disrupted, affecting translation.
Consider the specific effect mentioned in the problem: 'Pre-mRNA does not have introns removed.' This suggests a problem with RNA splicing, which is carried out by the spliceosome. The spliceosome requires snRNA, which is partially synthesized by RNA polymerase II.
Match the mutation to the effect: A mutation in RNA polymerase II could lead to defective snRNA synthesis, which in turn would impair the spliceosome's ability to remove introns from pre-mRNA. This explains the observed effect.
Summarize the relationships: RNA polymerase I mutation affects rRNA synthesis, RNA polymerase II mutation affects pre-mRNA and snRNA synthesis (leading to splicing defects), and RNA polymerase III mutation affects tRNA and 5S rRNA synthesis. The specific effect of introns not being removed from pre-mRNA is linked to RNA polymerase II mutation.

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Key Concepts

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

Eukaryotic RNA Polymerases

Eukaryotic cells contain three main types of RNA polymerases: RNA polymerase I, II, and III. RNA pol I primarily synthesizes ribosomal RNA (rRNA), RNA pol II is responsible for synthesizing messenger RNA (mRNA) and some small nuclear RNAs (snRNAs), while RNA pol III synthesizes transfer RNA (tRNA) and other small RNAs. Understanding the specific functions of each polymerase is crucial for predicting the effects of mutations.
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Mutations and Their Effects

Mutations are changes in the DNA sequence that can affect gene function. Depending on the type of mutation (e.g., missense, nonsense, or frameshift), the resulting protein may be altered in structure and function, potentially leading to various cellular effects. In the context of RNA polymerases, mutations can disrupt transcription processes, leading to issues such as incomplete RNA synthesis or failure to remove introns from pre-mRNA.
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Pre-mRNA Processing

Pre-mRNA processing is a critical step in eukaryotic gene expression, involving the removal of non-coding sequences (introns) and the joining of coding sequences (exons). This process is essential for producing mature mRNA that can be translated into proteins. If mutations affect the RNA polymerases involved in this processing, it can result in pre-mRNA that retains introns, leading to dysfunctional proteins and impaired cellular functions.
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Related Practice
Textbook Question

DNA footprint protection is a method that determines whether proteins bind to a specific sample of DNA and thus protect part of the DNA from random enzymatic cleavage by DNase I. A 400-bp segment of cloned DNA is thought to contain a promoter. The cloned DNA is analyzed by DNA footprinting to help determine if it has the capacity to act as a promoter sequence. The accompanying gel has two lanes, each containing the cloned 400-bp DNA fragment treated with DNase I to randomly cleave unprotected DNA. Lane 1 is cloned DNA that was mixed with RNA polymerase II and several TFII transcription factors before exposure to DNase I. Lane 2 contains cloned DNA that was exposed only to DNase I. RNA pol II and TFIIs were not mixed with that DNA before adding DNase I. Approximately what length is the DNA region protected by RNA pol II and TFIIs?

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Textbook Question

DNA footprint protection is a method that determines whether proteins bind to a specific sample of DNA and thus protect part of the DNA from random enzymatic cleavage by DNase I. A 400-bp segment of cloned DNA is thought to contain a promoter. The cloned DNA is analyzed by DNA footprinting to help determine if it has the capacity to act as a promoter sequence. The accompanying gel has two lanes, each containing the cloned 400-bp DNA fragment treated with DNase I to randomly cleave unprotected DNA. Lane 1 is cloned DNA that was mixed with RNA polymerase II and several TFII transcription factors before exposure to DNase I. Lane 2 contains cloned DNA that was exposed only to DNase I. RNA pol II and TFIIs were not mixed with that DNA before adding DNase I. What additional genetic experiments would you suggest to verify that this region of cloned DNA contains a functional promoter?

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Textbook Question

Suppose you have a 1-kb segment of cloned DNA that is suspected to contain a eukaryotic promoter, including a TATA box, a CAAT box, and an upstream GC-rich sequence. The clone also contains a gene whose transcript is readily detectable. Your laboratory supervisor asks you to outline an experiment that will (1) determine if eukaryotic transcription factors (TF) bind to the fragment and, if so, (2) identify where on the fragment the transcription factors bind. All necessary reagents, equipment, and experimental know-how are available in the laboratory. Your assignment is to propose techniques to be used to address the two items your supervisor has listed and to describe the kind of results that would indicate binding of TF to the DNA and the location of the binding.

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Textbook Question

Assume that a mutation affects the gene for each of the following eukaryotic RNA polymerases. Match each mutation with the possible effects from the list provided. More than one effect is possible for each mutation.

Some pre-mRNA is not synthesized.

476
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Textbook Question

Assume that a mutation affects the gene for each of the following eukaryotic RNA polymerases. Match each mutation with the possible effects from the list provided. More than one effect is possible for each mutation.

Some rRNA is not synthesized.

476
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Textbook Question

Assume that a mutation affects the gene for each of the following eukaryotic RNA polymerases. Match each mutation with the possible effects from the list provided. More than one effect is possible for each mutation.

Some tRNA is not synthesized.

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