Molecular Biology Chapter on Transcription

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Questions and Answers

Which step in gene expression involves the physical arrangement of DNA?

Protein degradation

Packing/unpacking of DNA (correct)

Transcription

Translation

What is the primary function of RNA polymerase during transcription?

Synthesize proteins

Transport mRNA to the ribosome

Stabilize mRNA after transcription

Read the DNA template strand (correct)

What is the correct order of transcription phases in bacteria?

Initiation, elongation, termination (correct)

Initiation, termination, elongation

Termination, elongation, initiation

Elongation, initiation, termination

Which strand of DNA is used as a template during transcription?

Template strand Signup and view all the answers

What is the main job of DNA as the genetic material?

To replicate and control cellular development. Signup and view all the answers

How is the synthesis of mRNA carried out from the DNA template?

Via condensation reactions Signup and view all the answers

Which type of RNA is transcribed but not translated into protein?

tRNA Signup and view all the answers

Which process directly involves the conversion of DNA sequence into mRNA?

Transcription Signup and view all the answers

During transcription in eukaryotes, which enzymes are primarily involved?

Nuclear RNA polymerase Signup and view all the answers

What role does the sigma subunit of bacterial RNA polymerase play?

Regulating transcription initiation Signup and view all the answers

What is meant by 'activated' ribonucleotide monomers in transcription?

Ribonucleotides with high energy phosphate bonds Signup and view all the answers

What is the role of small nuclear ribonucleoproteins (snRNPs) in mRNA processing?

To assist in the maturation of mRNA. Signup and view all the answers

Which statement about prokaryotic transcription is correct?

It occurs directly in the cytoplasm. Signup and view all the answers

In the context of the central dogma, which sequence correctly represents the flow of genetic information?

DNA → RNA → Protein Signup and view all the answers

Which of the following statements about RNA modifications is true?

They include capping and polyadenylation in eukaryotes. Signup and view all the answers

What is indicated by the term 'gene organization' in transcription?

The specific arrangement of DNA and its regulatory elements. Signup and view all the answers

What is the primary role of trans-acting factors in gene transcription?

To modulate the frequency of transcription initiation Signup and view all the answers

Which of the following describes the relationship between general transcription factors and core promoter elements?

General transcription factors bind to core promoter elements to initiate transcription. Signup and view all the answers

What is the function of RNA polymerase II in eukaryotic transcription initiation?

It is recruited by TFIIF to bind the promoter site. Signup and view all the answers

What type of elements do enhancer regions primarily recruit to enhance transcription?

Specific transcription factors Signup and view all the answers

Which of the following compounds inhibits the function of RNA polymerase II?

α-amanitin Signup and view all the answers

Which transcription factor is considered a trans-acting factor?

c-Myc Signup and view all the answers

What is the purpose of proximal regulatory elements like CAAT and GC boxes?

To provide binding sites for general transcription factors. Signup and view all the answers

Which statement accurately reflects transcription initiation in eukaryotes?

Transcription initiation requires specific transcription factors and RNA polymerase II. Signup and view all the answers

What is the role of the sigma subunit in bacterial transcription initiation?

Recognizes promoter regions of DNA. Signup and view all the answers

Which two regions are important bacterial promoter regions recognized by the sigma subunit?

-10 box and -35 box Signup and view all the answers

What happens after the DNA double helix is opened during transcription initiation?

Ribonucleotides begin to be added to the growing mRNA transcript. Signup and view all the answers

What triggers the termination of transcription in bacterial cells?

RNA polymerase encounters a termination signal coding for a hairpin loop structure. Signup and view all the answers

Which of the following mutations would most likely affect the rate of transcription?

A mutation in the -35 box region. Signup and view all the answers

During the elongation phase of transcription, which of the following actions occur?

Ribonucleotides are added to the growing mRNA strand. Signup and view all the answers

What is the initial point of contact for the RNA polymerase holoenzyme during transcription initiation?

The -35 nucleotides. Signup and view all the answers

What occurs after initiation of transcription is complete?

Sigma dissociates from the core enzyme. Signup and view all the answers

What does RNA polymerase I synthesize?

28S, 18S, and 5.8S rRNA precursors Signup and view all the answers

Which type of RNA polymerase synthesizes mRNA precursors?

RNA polymerase II Signup and view all the answers

What is the role of transcription factors in the transcription process?

They initiate or regulate transcription by binding to DNA sequences. Signup and view all the answers

Which of the following statements is true regarding chromatin remodeling?

Heterochromatin is transcriptionally inactive. Signup and view all the answers

What type of factors are classified as general transcription factors?

Factors that assist in the assembly of the transcription initiation complex. Signup and view all the answers

Which transcription factor is specifically associated with RNA polymerase II?

TFIID Signup and view all the answers

Which of the following is NOT a substrate required for eukaryotic RNA transcription?

Deoxyribonucleoside Triphosphates (dNTPs) Signup and view all the answers

What is the primary difference between general and specific transcription factors?

General transcription factors participate in all gene transcription while specific ones regulate particular genes. Signup and view all the answers

Study Notes

Learning Objectives

Understand the transcription process of DNA into messenger RNA (mRNA) for protein synthesis.
Describe transcription aspects: gene organization, transcription direction, transcription factors, and enzymes involved in prokaryotes and eukaryotes.
Identify RNA modifications and the role of small nuclear ribonucleoproteins (snRNPs) in mRNA maturation.

Central Dogma of Molecular Biology

Describes the flow of genetic information: DNA → RNA → Protein.
Includes processes: replication, transcription, and translation.
Highlights the importance of both transcriptional and translational control in gene expression.

Gene Expression

Conversion of gene's coded information into functional cellular structures.
Involves genes that are transcribed into mRNA, which may be translated into proteins, as well as those that produce non-coding RNAs (e.g., tRNA, rRNA).

Transcription in Bacteria

Transcription requires RNA polymerase to synthesize mRNA from a DNA template.
Consists of three phases: initiation, elongation, and termination.
mRNA is synthesized in the 5' to 3' direction using the template strand of DNA.

Initiation of Transcription in Bacteria

Begins at promoter regions (-35 box and -10 Pribnow box) where sigma subunit aids RNA polymerase binding.
Opening of the DNA helix allows for mRNA synthesis.
Sigma subunit dissociates once transcription begins.

Elongation and Termination in Bacterial Transcription

The RNA polymerase core enzyme continues to add ribonucleotides to the growing mRNA strand.
Termination occurs when RNA polymerase encounters a termination signal, leading to the formation of a hairpin loop in the RNA, causing polymerase to detach.

Eukaryotic Transcription Requirements

Involves three types of RNA polymerases:
- RNA polymerase I: Synthesizes rRNA.
- RNA polymerase II: Synthesizes mRNA and non-coding RNAs (snRNA, miRNA).
- RNA polymerase III: Synthesizes tRNA and some rRNA.
Requires DNA template, transcription factors, and substrates (rNTPs).

Transcription Factors in Eukaryotes

Essential for initiating and regulating transcription; classified as general and specific transcription factors.
General transcription factors work with RNA polymerase to form the transcription initiation complex.
Specific transcription factors modulate gene-specific transcription responses.

Transcription Process in Eukaryotes

Cannot occur without RNA polymerase II binding to a promoter, facilitated by TFIID.
Other factors, such as TFIIF and TFIIH, assist in transcription initiation and DNA unwinding.
Genes are transcribed individually from their own promoters.

Clinical Significance

α-amanitin (from Amanita phalloides) inhibits RNA polymerase II, affecting mRNA synthesis.
Actinomycin D inhibits transcription by intercalating DNA, utilized in cancer treatment.

Post-Transcriptional Modifications

Involves changes to pre-mRNA, including capping, polyadenylation, and splicing.
snRNPs play a critical role in removing introns and maturing mRNA for translation.

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Description

This quiz focuses on key concepts in the molecular biology of gene expression, specifically the transcription phase. It covers the role of RNA polymerase, the arrangement of DNA, and the process of mRNA synthesis. Test your understanding of these fundamental biological processes!