1001(L18)-Transcription
48 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is a key difference between RNA and DNA?

  • RNA uses ribose sugar while DNA uses deoxyribose. (correct)
  • RNA has a more stable structure than DNA.
  • RNA contains Thymine as a base while DNA contains Uracil.
  • RNA is double-stranded while DNA is single-stranded.

What are the components of ribonucleotides?

  • Nucleoside, ribose, and nucleotide
  • Base, sugar, and phospholipid
  • Deoxyribose, base, and phosphate
  • Heterocyclic base, sugar, and phosphate (correct)

Which statement about Uracil in RNA is true?

  • Uracil replaces Thymine in base-pairing. (correct)
  • Uracil is more stable than Thymine.
  • Uracil pairs with Cytosine.
  • Uracil does not pair with Adenine.

What kind of bond links nucleotides in RNA?

<p>3',5'-phosphodiester bonds (C)</p> Signup and view all the answers

Which of the following statements is true about RNA structure?

<p>RNA can form complex structures by folding. (D)</p> Signup and view all the answers

During transcription, which process follows initiation?

<p>Elongation (C)</p> Signup and view all the answers

Which of the following components is not directly involved in RNA synthesis?

<p>Ribosome (C)</p> Signup and view all the answers

What role do consensus sequences play in transcription?

<p>They help recognize promoters for transcription initiation. (A)</p> Signup and view all the answers

What is the primary structural feature that enhances DNA stability compared to RNA?

<p>Double helix structure (C)</p> Signup and view all the answers

Which type of RNA is primarily responsible for coding proteins?

<p>mRNA (C)</p> Signup and view all the answers

What distinguishes RNA's susceptibility to hydrolysis from DNA?

<p>Presence of a hydroxyl group on the 2' carbon (B)</p> Signup and view all the answers

Which type of RNA functions as an adaptor between mRNA and protein?

<p>tRNA (C)</p> Signup and view all the answers

Which statement about RNA structures is correct?

<p>RNA can form complex tertiary structures (C)</p> Signup and view all the answers

In terms of molecular weight, how is 1kb of mRNA related to protein coding?

<p>1kb of mRNA codes for about 30kD protein (A)</p> Signup and view all the answers

Which types of RNA are classified as non-coding RNAs?

<p>snoRNA and snRNA (B)</p> Signup and view all the answers

What is the measurement unit for RNA size?

<p>Kilobases (kb) (A)</p> Signup and view all the answers

What effect does the presence of an OH group on Carbon 2 of ribose have on RNA?

<p>Causes RNA to be unstable (D)</p> Signup and view all the answers

Which type of nucleoside triphosphate is more abundant in a cell?

<p>NTPs (ribonucleic acids) (C)</p> Signup and view all the answers

Which enzyme is responsible for synthesizing RNA during transcription?

<p>RNA polymerase (C)</p> Signup and view all the answers

During transcription, RNA synthesis occurs in which direction?

<p>5’ to 3’ (C)</p> Signup and view all the answers

What unique characteristic does RNA polymerase possess regarding the DNA template?

<p>It only transcribes one DNA strand (template strand) (A)</p> Signup and view all the answers

Which statement about RNA polymerase in E. coli is false?

<p>It consists of multiple subunits (C)</p> Signup and view all the answers

Where is the promoter of a gene located in relation to the gene itself?

<p>5’ of the gene (C)</p> Signup and view all the answers

What is the error rate for RNA polymerase during RNA transcription?

<p>Approximately 1 x 10-4 (B)</p> Signup and view all the answers

What is the significance of E.coli in biotechnology?

<p>It is used for the production of recombinant proteins. (B)</p> Signup and view all the answers

Which term describes a collection of genes regulated by the same stimulus?

<p>Stimulon (D)</p> Signup and view all the answers

What is the primary enzyme responsible for transcription in bacteria?

<p>RNA polymerase (B)</p> Signup and view all the answers

What is the function of transcriptional activators?

<p>To increase the number of transcripts by facilitating RNA polymerase binding. (A)</p> Signup and view all the answers

What is the role of the promoter in transcription?

<p>It is where RNA polymerase binds to begin transcription. (C)</p> Signup and view all the answers

Which of the following describes an operon?

<p>One or more genes transcribed together under one regulatory site. (A)</p> Signup and view all the answers

Which of the following antibiotics specifically targets transcription?

<p>All of the above (D)</p> Signup and view all the answers

What is the chain growth direction during RNA synthesis?

<p>5′ to 3′ (B)</p> Signup and view all the answers

What is the primary role of the promoter in transcription?

<p>It is a region of DNA where transcription factors can bind. (A)</p> Signup and view all the answers

What components make up the core RNA polymerase in E.coli?

<p>2 α, 1 β, 1 β’, and 1 ω (C)</p> Signup and view all the answers

What are consensus sequences in the context of bacterial promoters?

<p>Conserved nucleotide sequences determined by sequence comparison. (C)</p> Signup and view all the answers

What role does the sigma factor play in RNA polymerase activity?

<p>It recognizes and binds to promoter regions. (D)</p> Signup and view all the answers

Which of the following is true about polycistronic mRNA?

<p>It contains coding sequences for multiple proteins. (C)</p> Signup and view all the answers

What are the highly conserved sequences within the promoter that RNA polymerase binds to?

<p>-35 and -10 regions (C)</p> Signup and view all the answers

How are different sigma factors significant in bacterial gene expression?

<p>They allow expression of specific groups of genes. (B)</p> Signup and view all the answers

What is the Pribnow box known for?

<p>It is the conserved -10 region of bacterial promoters. (D)</p> Signup and view all the answers

What is the primary role of the sigma factor s70 in E.coli?

<p>To mediate the binding of RNA polymerase to specific promoters (B)</p> Signup and view all the answers

Which of the following sequences is part of the s70 promoter in E.coli?

<p>TTGACA (B)</p> Signup and view all the answers

What is the role of transcriptional activators in relation to RNA polymerase containing s70?

<p>They stabilize the binding to the promoter (D)</p> Signup and view all the answers

How does the sigma factor s38 differ from s70 in Escherichia coli?

<p>s38 is specific for genes expressed during stationary phase (C)</p> Signup and view all the answers

What can inhibit the activity of sigma factors like s70 in E.coli?

<p>Anti-sigma factors and proteins that regulate synthesis or degradation (C)</p> Signup and view all the answers

What is the approximate size of the sigma factor s70?

<p>70 kDa (D)</p> Signup and view all the answers

What is one function of domain 2.3 in sigma factor s70?

<p>To mediate binding to the -10 element (B)</p> Signup and view all the answers

How many different sigma factors are known to exist in E.coli?

<p>Seven (D)</p> Signup and view all the answers

Flashcards

RNA Secondary Structures

RNA, though single-stranded, can fold into complex structures like stem-loops and bulges due to base pairing and tertiary interactions.

Stem-Loop

A common RNA secondary structure formed by a sequence of complementary bases pairing. Stem loops have a double-stranded region (stem) and a single-stranded loop.

Bulge

An RNA secondary structure where a single unpaired base protrudes outward from a double-stranded region.

Tertiary Interaction

Complex interactions between different parts of folded RNA, contributing to its overall three-dimensional structure.

Signup and view all the flashcards

How is DNA size measured?

Double-stranded DNA size is measured in base pairs (bp). 1000bp = 1kbp, 1000kb = 1Mbp.

Signup and view all the flashcards

How is RNA size measured?

RNA size is measured in bases (b). 1000b = 1kb.

Signup and view all the flashcards

DNA vs RNA Stability

DNA is more stable than RNA due to its double-stranded structure and repair mechanisms. RNA is less stable due to its single-stranded nature and the presence of a reactive 2' OH group.

Signup and view all the flashcards

Classes of RNA

Cells produce various types of RNA, each with a specific function. These include mRNA (messenger), rRNA (ribosomal), tRNA (transfer), snRNA (small nuclear), snoRNA (small nucleolar), and others.

Signup and view all the flashcards

Operon

A group of genes transcribed together into a single mRNA molecule, controlled by a single regulatory site.

Signup and view all the flashcards

Regulon

A set of operons that are controlled as a unit by a single regulatory mechanism.

Signup and view all the flashcards

Stimulon

A collection of genes, including those within operons and regulons, that are regulated by the same stimulus.

Signup and view all the flashcards

Transcription

The process of copying genetic information from DNA to RNA.

Signup and view all the flashcards

RNA polymerase

The enzyme responsible for transcribing DNA into RNA.

Signup and view all the flashcards

Promoter

The specific DNA sequence where RNA polymerase binds to start transcription.

Signup and view all the flashcards

Operator

A DNA sequence that binds transcription factors, regulating gene expression.

Signup and view all the flashcards

Transcription terminator

A DNA sequence that signals the end of transcription, causing RNA polymerase to release the RNA molecule.

Signup and view all the flashcards

Transcribed Region

The portion of DNA that is actually copied into mRNA during transcription.

Signup and view all the flashcards

Terminator

A sequence of DNA that tells RNA polymerase to stop copying the gene, marking the end of a gene.

Signup and view all the flashcards

Consensus Sequence

A common sequence of nucleotides found in multiple promoters that help RNA polymerase recognize and bind to the promoter.

Signup and view all the flashcards

RNA Polymerase Holoenzyme

The complete form of RNA polymerase, which includes the core enzyme and a sigma factor.

Signup and view all the flashcards

Sigma Factor

A protein subunit of RNA polymerase responsible for identifying and binding to the promoter.

Signup and view all the flashcards

Pribnow Box

A short sequence of nucleotides within the -10 region of a bacterial promoter that helps RNA polymerase bind.

Signup and view all the flashcards

Abundance of dNTPs vs. NTPs

NTPs (ribonucleotides) are more abundant in cells than dNTPs (deoxyribonucleotides) because they are used in many processes, like RNA synthesis and energy metabolism.

Signup and view all the flashcards

Error Rates: DNA vs. RNA Polymerases

RNA polymerases have a higher error rate (~1 x 10-4) than DNA polymerases, meaning they make more mistakes during transcription.

Signup and view all the flashcards

E.coli RNA Polymerase

E.coli RNA polymerase has multiple subunits and requires a Sigma factor to recognize and bind to specific promoter sequences within the DNA to start transcription.

Signup and view all the flashcards

Promoter Location

The promoter sequence of a gene is located upstream (5') of the gene on the same DNA strand, indicating the starting point for transcription.

Signup and view all the flashcards

Transcription Ingredients

Transcription requires a DNA template, ribonucleotides (rNTPs), and the enzyme RNA polymerase to synthesize RNA.

Signup and view all the flashcards

Key Features of Transcription

Transcription makes RNA from DNA, synthesizing a new RNA molecule from a DNA template. The process is 5' to 3' direction, doesn't require a primer, and has a higher error rate compared to replication.

Signup and view all the flashcards

Sense vs. Antisense Strands

During transcription, RNA is synthesized from the antisense strand (template strand) of DNA, which is complementary to the sense strand, which has the same sequence as mRNA.

Signup and view all the flashcards

What is the major sigma factor in E. coli?

The primary sigma factor in E. coli is σ70, also known as the 70kDa sigma factor. It's responsible for normal gene expression.

Signup and view all the flashcards

What is the role of σ70 in promoter recognition?

σ70 recognizes and binds to specific DNA sequences in the promoter region, called the -10 and -35 elements. These sequences are crucial for RNA polymerase to initiate transcription.

Signup and view all the flashcards

What are alternative sigma factors?

Alternative sigma factors are different types of sigma factors that recognize different consensus sequences in promoters. They allow E. coli to regulate gene expression in response to specific environmental conditions.

Signup and view all the flashcards

What is the function of σ32?

σ32 is an alternative sigma factor that recognizes promoters of genes involved in the heat shock response. It helps the cell respond to stressful conditions like high temperature.

Signup and view all the flashcards

What is the function of σ54?

σ54 is another alternative sigma factor that recognizes promoters of genes involved in nitrogen metabolism. It helps regulate genes for utilizing nitrogen efficiently.

Signup and view all the flashcards

What is the role of anti-sigma factors?

Anti-sigma factors are proteins that can bind to and block the activity of sigma factors. They regulate the activity of sigma factors by preventing them from binding to RNA polymerase.

Signup and view all the flashcards

How is the activity of sigma factors regulated?

The activity of sigma factors can be regulated by various mechanisms, including the synthesis and degradation of the sigma factor, binding of anti-sigma factors, and the presence of specific regulatory proteins.

Signup and view all the flashcards

What is the main function of sigma factors in E.coli?

Sigma factors are key for gene regulation in E. coli. They determine which genes are transcribed by binding to specific promoter regions and guiding RNA polymerase.

Signup and view all the flashcards

RNA vs DNA: Key Difference?

RNA is single-stranded, uses ribose sugar, and has uracil (U) instead of thymine (T).

Signup and view all the flashcards

Transcription Initiation

RNA polymerase binds to the promoter, unwinds DNA, and starts making RNA.

Signup and view all the flashcards

Transcription Elongation

RNA polymerase moves along the DNA, adding ribonucleotides to the growing RNA chain.

Signup and view all the flashcards

Study Notes

Lecture 18: RNA Synthesis - Transcription

  • Lecture delivered by Dr. Dinesh Balachandra, Lecturer (Non-Clinical), Biomedical Sciences, NUMed Malaysia.
  • Email address provided, but excluded as per instructions.
  • Previous lecture topics (L14-17) included DNA constituents (phosphate, deoxyribose, bases, nucleosides, nucleotides), Chargaff's rules, base pairing, DNA structure (fibre diffraction patterns and the Watson-Crick model), and DNA sequencing technologies.

RNA Synthesis: Transcription

  • DNA undergoes transcription to produce mRNA.
  • mRNA is then used to synthesize proteins.
  • The process involves a biological function.

What to Understand from Lecture 18

  • Understanding the components of the system for RNA synthesis (RNA polymerase and sigma factors).
  • Understanding promoters and consensus sequences.
  • Understanding transcription initiation, elongation, and termination stages.

RNA Structure

  • Images of RNA structure were presented.

RNA Characteristics

  • Chemically similar to DNA, but differing in key aspects.
  • Single-stranded, but can fold into complex structures.
  • Uses ribose instead of deoxyribose in its backbone, making it less stable.
  • Employs uracil (U) in place of thymine (T).

Ribonucleotides Components

  • Heterocyclic bases (adenine, guanine, cytosine, uracil, and thymine).
  • Sugar (ribose or deoxyribose).
  • Phosphate.
  • DNA uses A, G, C, T and deoxyribose.
  • RNA uses A, G, C, U and ribose.

Polymeric Structure of DNA and RNA

  • 3',5'-phosphodiester bonds form the polymer backbone.

RNA Forms Secondary Structures

  • Uracil replaces thymine in base pairing (U-A base pairs).
  • Non-Watson-Crick base pairs are also common in RNA structures.
  • Image shows RNA structure.

RNA Size Measurement

  • Double-stranded DNA is measured in base pairs (bp). 1000 bp = 1 kbp, 1000 kbp = 1 Mbp
  • RNA is measured in bases (b). 1000 b = 1 kb
  • 1 kb of mRNA codes for approximately 30 kD protein.

DNA vs RNA Stability

  • DNA is more stable than RNA due to its double-helix structure and the presence of repair mechanisms in the nucleus.
  • RNA is less stable and is susceptible to hydrolysis due to the presence of an OH group at the 2' carbon of the ribose sugar.

Classes of RNA Produced in Cells

  • mRNA: encodes proteins.
  • rRNA: structural component of ribosomes.
  • tRNA: adapts information between mRNA and proteins.
  • snRNA: involved in nuclear functions, including mRNA splicing.
  • snoRNA: processes/modifies rRNA.
  • Other RNAs involved in various cellular processes like telomeres, gene inactivation, and protein transport to the ER.

Transcription in E. coli

  • Illustrated diagram showing the process including promoter, transcribed region, and terminator.
  • mRNA can be polycistronic.

Transcription Promoters- Reminder

  • Promoter: located upstream (5') of a gene.
  • Contains specific nucleotide sequences for transcription factor association.
  • Transcription factors recruit RNA polymerase.
  • Conserved regions (consensus sequences) are identified.

How Consensus Sequences are Determined

  • Determined by sequence comparison across different promoters.
  • Diagrams and examples of promoter regions across various sequences are shown.

Identifying Consensus Sequences in Bacterial Promoters

  • Data presented in table and figure format to show consensus sequences and distances.

E. coli RNA Polymerase

  • Multisubunit enzyme, composed of core enzyme (β, β′, α, ω) and σ factor, to form the holoenzyme.

Transcription- RNA Polymerase

  • Core enzyme consists of 5 different subunits(β,β′, α, ω).
  • Sigma factor binds to the promoter.
  • Promoter region has highly conserved -35 and -10 sequences.

Sigma Factors

  • Different sigma factors allow the expression of different genes.
  • Sigma factor σ70 is the common one.
  • Other factors (σ38, σ32, σ28, σ24, σ19) exist for particular circumstances (stress response, stationary phase, etc.).

The E. coli σ70 Promoter

  • Diagram emphasizing the -35 and -10 consensus sequences.

Domains of σ70

  • Functions of the different domains (N- and C-terminal domains).

Alternative Sigma Factors

  • Alternative factors (e.g., σ38) are used for specific occasions and circumstances.

Termination

  • RNA polymerase stops transcription at terminator sequences.
  • Two types of termination (factor-independent and rho-dependent).

Factor-Independent Termination

  • Formation of a stem-loop structure in the newly synthesized RNA (complementary base-pairing).

Rho-Dependent Termination

  • Rho protein factor unwinds the RNA:DNA hybrid.

What We Covered Today (L18)

  • RNA structure.
  • Components of RNA synthesis (RNA polymerase, sigma factors, promoters, consensus sequences).
  • Transcription (initiation, elongation, termination).

Next Lecture (L19)

  • How transcription (and therefore gene expression) is controlled.

Points for Revision

  • Promoter definition, location and key sequence elements.
  • Consensus sequence definition.
  • Promoter influence on strength.
  • Core RNA polymerase subunit composition.
  • Promoter recognition subunit and related names.
  • Transcription initiation closed vs. open complex.
  • Sigma factor release time from RNA polymerase.
  • Transcription elongation process.
  • How self-complementary sequences drive termination.
  • Rho factor definition and function.

Further Reading

  • References to specific textbook chapters and online resources for further studies about RNA, transcription (and relevant topics) are recommended. Note: URLs are excluded as per instructions.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

RNA Synthesis Lecture Notes PDF

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser