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.

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.
2. 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.
3. 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.
4. 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.
5. 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.

Key Concepts

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.

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.

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.