Eukaryotic Promoters and RNA Polymerases

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What are the two most common core promoters in protein-encoding genes?

The TATA box and the Inr (Initiator) element

What is the role of chromatin-remodeling complexes in eukaryotic transcription?

To alleviate repression due to nucleosomes by mediating ATP-dependent conformational changes in nucleosome structure

What is the function of the Mediator complex in transcription initiation?

To allow RNA polymerase II to communicate with transcriptional activators bound at sites distant from the promoter

What are the two sets of factors that are important for activation of eukaryotic transcription?

Chromatin-remodeling complexes and histone-modifying enzymes Signup and view all the answers

What is the role of general transcription factors in the assembly of the preinitiation complex (PIC)?

To bind to the promoter and recruit RNA polymerase II to initiate transcription Signup and view all the answers

What is the primary difference between the three classes of RNA polymerases in eukaryotes?

The primary difference is in the type of genes they transcribe, with Pol I transcribing rRNA genes, Pol II transcribing mRNA genes, and Pol III transcribing tRNA genes and a few other types of RNA. Signup and view all the answers

What is the significance of α-amanitin in the study of eukaryotic transcription?

α-amanitin is a toxin that inhibits RNA polymerase II, and its sensitivity is used to distinguish between the three classes of RNA polymerases in eukaryotes. Signup and view all the answers

How do the subunits of RNA polymerases in eukaryotes compare to those in prokaryotes?

The subunits of RNA polymerases in eukaryotes have sequences similar to the β and β' subunits of E. coli RNA polymerase, indicating evolutionary conservation of the catalytic site. Signup and view all the answers

What is the functional significance of the large size of RNA polymerases in eukaryotes?

The large size of RNA polymerases in eukaryotes is likely related to their complex regulatory roles, including interactions with transcription factors and chromatin-modifying enzymes. Signup and view all the answers

How do the three classes of RNA polymerases in eukaryotes relate to each other evolutionarily?

The three classes of RNA polymerases in eukaryotes share conserved catalytic sites, indicating a common ancestral origin, but have diverged to specialize in transcribing different types of genes. Signup and view all the answers

What is the role of leader peptides in transcription attenuation, and how does this mechanism regulate gene expression in prokaryotes?

Leader peptides play a crucial role in transcription attenuation by binding to the ribosome, which in turn affects the secondary structure of the mRNA, thereby regulating gene expression in prokaryotes. Signup and view all the answers

How do operons regulate gene expression in prokaryotes, and what are the advantages of this type of regulation?

Operons regulate gene expression in prokaryotes by controlling the transcription of multiple genes involved in a specific metabolic pathway, and the advantages include efficient regulation of gene expression and rapid adaptation to changes in the environment. Signup and view all the answers

What is the role of amino acid biosynthesis in the regulation of gene expression, and how do feedback inhibition and repression mechanisms contribute to this regulation?

Amino acid biosynthesis regulates gene expression by providing feedback inhibition and repression mechanisms that prevent the overproduction of amino acids, thereby maintaining a balanced metabolic state. Signup and view all the answers

What is post-transcriptional regulation, and how do mechanisms such as RNA splicing, editing, and degradation regulate gene expression?

Post-transcriptional regulation refers to the control of gene expression after transcription, and mechanisms such as RNA splicing, editing, and degradation regulate gene expression by modifying or degrading RNA molecules. Signup and view all the answers

How do chromatin remodeling complexes regulate gene expression in eukaryotes, and what is the significance of this regulation?

Chromatin remodeling complexes regulate gene expression in eukaryotes by modifying chromatin structure, allowing or blocking access to transcription factors, and this regulation is significant because it allows for dynamic changes in gene expression in response to environmental cues. Signup and view all the answers

What is the primary difference between transcription and translation in prokaryotes and eukaryotes?

In prokaryotes, transcription and translation occur simultaneously, whereas in eukaryotes, they are spatially separated, with transcription occurring in the nucleus and translation occurring in the cytoplasm. Signup and view all the answers

What is the purpose of transcript processing in eukaryotes?

Transcript processing converts the primary transcript into a mature mRNA, including the removal of introns and the splicing of exons. Signup and view all the answers

What is the significance of the fact that eukaryotic mRNAs are monocistronic?

Eukaryotic mRNAs encode only one polypeptide, unlike prokaryotic mRNAs, which can encode multiple polypeptides. Signup and view all the answers

What is the function of introns in eukaryotic genes?

Introns are non-coding regions that intervene between exons (protein-coding regions) in eukaryotic genes. Signup and view all the answers

What is the complexity of the mechanism by which introns are excised and exons are spliced together?

The mechanism is complex and must be precise to ensure the correct assembly of functional mRNA molecules. Signup and view all the answers