Exam 3 pt 1

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Questions and Answers

What is the primary role of RNA Polymerase II in eukaryotes?

Synthesizes tRNAs

Synthesizes most mRNAs (correct)

Synthesizes all types of RNA

Synthesizes most rRNAs

What feature distinguishes polycistronic mRNA in prokaryotes?

Contains multiple genes coding for proteins (correct)

Contains information for only one polypeptide

Requires multiple promoters for transcription

Requires a single transcription factor

What initiates transcription in eukaryotic cells?

Transcription factors (correct)

Rho factors

Introns

Sigma factors

What mechanism does Rho-dependent termination involve?

Binding of Rho to Rut sites and RNA Polymerase Signup and view all the answers

Which statement about the genetic code is accurate?

One amino acid can be encoded by multiple codons Signup and view all the answers

What is a common characteristic of intrinsic terminators?

They rely on inverted repeat sequences Signup and view all the answers

What type of RNA carries the genetic message after introns have been removed?

mRNA Signup and view all the answers

How do prokaryotic cells differ from eukaryotic cells in terms of transcription initiation?

Prokaryotes use Sigma factors for initiation Signup and view all the answers

In prokaryotes, how are genes related to metabolic pathways typically organized?

Clusterd together in operons Signup and view all the answers

What does a promoter do in the context of transcription?

Binds RNA polymerase and initiates transcription Signup and view all the answers

What is the primary function of DNA binding proteins in transcriptional control?

To recognize specific sequences of DNA Signup and view all the answers

In transcriptional control, what is the role of a repressor?

To decrease the level of mRNA Signup and view all the answers

Which of the following defines an inducible pathway?

It is usually turned off and substrate turns it on. Signup and view all the answers

What is the function of a corepressor in bacterial regulatory proteins?

It activates repressor and allows binding. Signup and view all the answers

Which type of transcriptional control would involve the binding of an activator to an activator binding site?

Positive control Signup and view all the answers

What does transcriptional repression involve?

Binding of repressor proteins to operator sequences Signup and view all the answers

What characterizes a repressible pathway?

It is usually turned off and turned on by the presence of product. Signup and view all the answers

What is the role of an inducer in gene regulation?

To prevent repressor from binding to DNA Signup and view all the answers

Which of the following statements about allosteric DNA binding proteins is correct?

They bind both DNA and an effector molecule. Signup and view all the answers

What is the main difference between negative and positive control in transcription?

Negative control decreases mRNA levels while positive control increases them. Signup and view all the answers

Study Notes

Transcription Unit

In prokaryotes, the transcription unit can contain multiple genes, resulting in polycistronic mRNA.
These genes often code for enzymes involved in the same metabolic pathway.

Eukaryotic Transcription

Eukaryotes have three types of RNA polymerases: RNA Polymerase I, II, and III.
Each polymerase is responsible for producing a specific type of RNA, such as rRNA, mRNA, or tRNA.
Transcription in eukaryotes is controlled by transcription factors instead of sigma factors.

Eukaryotic RNA Processing

Eukaryotic mRNA undergoes post-transcriptional modification.
This process includes capping, splicing, and polyadenylation.

Transcription Termination in Prokaryotes

Rho-independent termination relies on specific DNA sequences called inverted repeats, which form hairpin structures in the RNA.
Rho-dependent termination requires the Rho protein, which binds to a specific site on the RNA and then moves towards the RNA polymerase.

Messenger RNA

Messenger RNA (mRNA) carries genetic information from DNA to the ribosomes.
In eukaryotes, mRNA undergoes splicing to remove introns and leave the coding exons.

The Genetic Code

The genetic code is a set of rules that determines how the sequence of nucleotides in DNA or RNA codes for the sequence of amino acids in proteins.
It is expressed in terms of codons, three nucleotide sequences.
Each codon specifies a particular amino acid.

Translation

Translation is the process by which the genetic code in mRNA is used to synthesize a protein.
This process occurs at the ribosomes.

Gene Regulation

Gene regulation refers to the control of gene expression, which can occur at different levels.
These levels include transcriptional, translational, and post-translational.
Constitutive genes are expressed at a constant level, while regulated genes are expressed only when needed.

Transcriptional Control

Transcriptional control often involves DNA-binding proteins that recognize specific sequences in DNA.
These proteins act as either repressors or activators.
Repressors decrease gene expression by binding to operators, while activators increase gene expression by binding to activator binding sites.

Inducible and Repressible Pathways

Inducible pathways are typically turned off and are activated by the presence of a substrate.
Repressible pathways are typically turned on and are repressed by the presence of a product.

Bacterial Regulatory Proteins

Bacterial regulatory proteins are often allosteric, meaning they can bind to both DNA and effector molecules.
Inducers prevent repressors from binding to DNA, while corepressors activate repressors, allowing them to bind to DNA.

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Description

This quiz covers the essential concepts of transcription in both prokaryotic and eukaryotic organisms. Topics include the transcription unit, types of RNA polymerases, RNA processing, and termination methods in prokaryotes. Test your knowledge on gene expression and regulatory mechanisms.