Molecular Biology Chapter on Gene Expression
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Questions and Answers

What is the role of ribozymes in cellular processes?

  • Ribozymes are involved in the replication of DNA.
  • Ribozymes have catalytic roles in processes such as RNA cutting, molecule replication, and protein bond formation. (correct)
  • Ribozymes are responsible for the transcription of DNA into RNA.
  • Ribosomes catalyze the formation of peptide bonds between amino acids in protein synthesis.

What percentage of the eukaryotic genome is made up of genes?

  • 1-1.5% (correct)
  • 50-60%
  • 10-15%
  • 90-95%

What is the main difference between DNA and RNA?

  • DNA is single-stranded, while RNA is double-stranded.
  • DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. (correct)
  • DNA is found in the cytoplasm, while RNA is found in the nucleus.
  • DNA is involved in protein synthesis, while RNA is involved in DNA replication.

What is the process of transcription?

<p>The synthesis of RNA from DNA. (C)</p> Signup and view all the answers

What are enhancers and silencers in the context of gene expression?

<p>Regions of DNA that regulate the rate of transcription. (C)</p> Signup and view all the answers

What is the function of RNA polymerase in the process of gene expression?

<p>To synthesize RNA from DNA. (B)</p> Signup and view all the answers

What is the term for the process where a single gene can produce multiple proteins?

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

What is the role of promoters in gene expression?

<p>Promoters are binding sites for RNA polymerase, initiating transcription. (C)</p> Signup and view all the answers

What is the primary location for the transcription of genes to RNA in eukaryotic cells?

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

What does gene expression primarily refer to?

<p>Production of RNA and proteins from a gene (A)</p> Signup and view all the answers

Which of the following statements about gene-to-protein relationships is correct?

<p>One gene encodes one polypeptide. (D)</p> Signup and view all the answers

Which class of RNA is not involved in protein synthesis?

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

What was the initial model proposed regarding gene function?

<p>One gene equals one enzyme. (C)</p> Signup and view all the answers

Which scientist is associated with the discovery of the molecular basis of phenotypes?

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

In eukaryotic gene expression, what is the significance of the process being compartmentalized?

<p>It facilitates regulation at multiple stages. (A)</p> Signup and view all the answers

What genetic condition is characterized by an inability to produce melanin?

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

What is the significance of the CCAAT box in RNA polymerase II promoters?

<p>It is a binding site for transcription factors. (B)</p> Signup and view all the answers

When does abortive initiation of transcription occur?

<p>When a 9-12nt long strand is synthesized. (A)</p> Signup and view all the answers

What happens to RNA polymerase II after it synthesizes a transcript of approximately 30 nucleotides?

<p>It leaves the promoter region to allow new RNA polymerase binding. (A)</p> Signup and view all the answers

What characterizes the open complex in transcription?

<p>The DNA strands are separated and positioned in the active site. (C)</p> Signup and view all the answers

How do transcription factors interact with RNA polymerase II during transcription?

<p>They assist in the recruitment of RNA polymerase II and are left behind after initiation. (D)</p> Signup and view all the answers

What is the role of RNA polymerase during transcription?

<p>It synthesizes RNA using a DNA template. (D)</p> Signup and view all the answers

Which strand of DNA serves as the template during transcription?

<p>The template strand. (B)</p> Signup and view all the answers

In which direction does transcription occur?

<p>5’ to 3’ direction on the coding strand. (D)</p> Signup and view all the answers

What are the three main stages of transcription?

<p>Initiation, elongation, and termination. (B)</p> Signup and view all the answers

What is found at the beginning of a transcription unit?

<p>A promoter region. (A)</p> Signup and view all the answers

What requirement must be fulfilled before transcription can initiate?

<p>Modification of chromatin structure. (D)</p> Signup and view all the answers

If the DNA strand used as a template is 5’–GTACCGTC–3’, what is the correct sequence of the transcribed RNA?

<p>5’–GUACCGUC–3’ (A)</p> Signup and view all the answers

What is the significance of the +1 nucleotide in a transcription unit?

<p>It is the first nucleotide that is transcribed. (B)</p> Signup and view all the answers

What is the primary role of the mediator complex in transcription regulation?

<p>To regulate the speed of transcription (B)</p> Signup and view all the answers

Which RNA polymerase is responsible for transcribing protein-coding genes in eukaryotes?

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

What is a gene primarily defined as?

<p>A sequence of DNA that functions as a unit. (A)</p> Signup and view all the answers

What is the significance of the TATA box in the core promoter?

<p>It is recognized by the TFIID transcription factor (B)</p> Signup and view all the answers

Which of the following correctly describes the interaction between transcription factors and enhancers?

<p>They can be located far from the gene they regulate (C)</p> Signup and view all the answers

What role do introns play in gene expression?

<p>They are spliced out before protein translation. (A)</p> Signup and view all the answers

Where is the promoter region typically located?

<p>Next to the transcription start site. (D)</p> Signup and view all the answers

Which statement about the structure of transcription machinery is true?

<p>It can include up to 50 different accessory proteins (C)</p> Signup and view all the answers

Which of the following statements about regulatory regions is true?

<p>They can be located very far from the regulated gene. (B)</p> Signup and view all the answers

What role do regulatory proteins play in transcription?

<p>They modify chromatin structure to facilitate transcription (B)</p> Signup and view all the answers

What is the purpose of splicing in the processing of RNA?

<p>To remove introns from the RNA transcript. (B)</p> Signup and view all the answers

How does RNA polymerase II differ from other RNA polymerases in eukaryotes?

<p>It transcribes genes encoding proteins (A)</p> Signup and view all the answers

What is required for eukaryotic RNA polymerase to recognize DNA sequences?

<p>Many accessory proteins and transcription factors are needed (B)</p> Signup and view all the answers

What is the termination region's role in a gene?

<p>To indicate the end of transcription. (C)</p> Signup and view all the answers

What is the longest human gene known to code for dystrophin?

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

Which nucleotide sequences decrease gene expression?

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

Flashcards

Eukaryotic Genes

Structures made of DNA that code for RNA and proteins in eukaryotes.

RNA Classes

Various types of RNA, each with distinct functions in the cell.

RNA Polymerase

Enzyme that synthesizes RNA from a DNA template during transcription.

Eukaryotic Transcription

The process of copying a gene's DNA sequence into RNA.

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Promoters and Enhancers

DNA sequences that help initiate and regulate the transcription process.

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RNA Processing

Modification of RNA after transcription, including splicing and capping.

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Alternative Splicing

A process that allows a single gene to produce multiple RNA variants.

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Intergenic Regions

Non-coding regions of DNA located between genes.

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Gene

A sequence of DNA that gives rise to RNA or protein.

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Eukaryotic gene structure

Eukaryotic genes include regulatory regions and coding regions.

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Regulatory regions

Nucleotide sequences that control gene expression.

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Promoter

A DNA sequence where proteins bind to start transcription.

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Termination region

The area in DNA signaling the end of transcription.

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Introns

Noncoding sections of RNA that are spliced out.

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Exons

Coding sections of RNA that remain after splicing.

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Splicing

The process of removing introns from the RNA transcript.

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Gene Expression

The process of producing RNA and proteins from a gene.

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Transcription

The copying of DNA information into RNA.

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mRNA

Messenger RNA that carries genetic information to ribosomes.

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One Gene - One Enzyme

Initial model stating one gene produces one specific enzyme.

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Polypeptide

A sequence of amino acids; a product of gene expression.

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Structural RNA Genes

Genes that encode RNA molecules, not proteins.

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Albinism

An inherited condition marked by lack of melanin production.

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George Beadle & Edward Tatum

Scientists who contributed to understanding gene function in protein synthesis.

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RNA Classes in Protein Synthesis

Three main RNA classes are involved in synthesizing proteins: mRNA, rRNA, and tRNA.

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Transcription Unit

A transcription unit includes a promoter, RNA coding region, and terminator.

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Template Strand

The strand of DNA used as a template for RNA synthesis during transcription.

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Transcription Direction

Transcription occurs in a 5' to 3' direction on the template strand.

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RNA Polymerase Function

RNA polymerase synthesizes RNA using a DNA template and does not require a primer.

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Transcription Stages

Transcription has three stages: initiation, elongation, and termination.

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Initiation of Transcription

Initiation is when transcription machinery binds to the promoter to start RNA synthesis.

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Termination of Transcription

Termination occurs when RNA polymerase dissociates from the DNA, releasing the newly synthesized RNA.

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CCAAT box

A regulatory element located upstream of eukaryotic promoters that helps initiate transcription.

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Open complex

The structure formed when DNA strands separate at the active site of RNA polymerase during transcription initiation.

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Abortive initiation

A phase where RNA polymerase synthesizes short RNA strands before elongation begins.

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Elongation

The phase of transcription where RNA polymerase moves downstream and extends the RNA strand.

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RNA polymerase II

An enzyme that synthesizes mRNA in eukaryotic cells during transcription.

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Accessory Proteins

Proteins that assist RNA polymerase in transcription initiation.

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Basal Apparatus

The complex formed by RNA pol II and general transcription factors for transcription.

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RNA Polymerases in Eukaryotes

Three main types (I, II, III) that transcribe different genes in eukaryotic cells.

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TATA Box

A core promoter sequence recognized by TFIID during transcription initiation.

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Transcription Factors (TFs)

Proteins that regulate the rate of transcription by binding to DNA.

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Regulatory Promoter

Part of the promoter that interacts with transcription factors to modulate transcription.

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Mediator Complex

A multi-protein complex that relays signals from transcription factors to RNA polymerase.

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Chromatin Structure

The organization of DNA in the nucleus that affects gene expression.

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Study Notes

Gene Expression: From DNA to RNA

  • Eukaryotic genes are organized into coding and regulatory regions
  • Genes control traits – transcribed into RNA, then translated into proteins
  • Only a small portion of the genome (1-1.5%) consists of genes
  • The set of expressed genes in a cell determines its function

Eukaryotic Gene Structure

  • Genes have regulatory and coding regions
  • Regulatory regions (e.g., promoter) control gene expression
  • Promoters are DNA sequences where proteins bind for transcription initiation.
  • Termination regions mark transcription's end.
  • Introns are non-coding sections of RNA transcripts that are removed, while exons code for functional products.
  • Splicing is the intron removal process.
  • The largest human gene (DMD) codes for dystrophin (79 exons, 2300 kb).

RNA Classes and Functions

  • Three main RNA classes are involved in protein synthesis: mRNA, rRNA, tRNA
  • mRNA carries genetic information from DNA to ribosomes for protein synthesis.
  • rRNA forms the ribosomal structure and facilitates translation.
  • tRNA brings amino acids to the ribosome to build the protein.

Transcription Stages

  • Transcription copies DNA information into RNA
  • Stages include Initiation, Elongation, and Termination
  • Initiation involves the transcription machinery binding to the promoter for synthesis.
  • Elongation involves RNA polymerase moving along the template and adding nucleotides.
  • Termination involves RNA polymerase detaching and releasing RNA.

RNA Polymerases

  • Eukaryotes have three main RNA polymerases (I, II, III)
  • Different polymerases transcribe different genes (e.g., RNA polymerase II transcribes protein-coding genes).

Transcription Regulation

  • Initiation involves many accessory proteins to bind to and recruit polymerase
  • Transcription factors (TFs) bind to specific DNA sequences.
  • Enhancers and silencers alter transcription rate—can be far from the transcribed gene.
  • Core promoters contain essential sequences (like TATA box) to help RNA polymerase bind.
  • Regulatory promoters influence transcription speed via mediators.
  • The basal transcription apparatus consists of RNA pol II plus other proteins.
  • DNA and RNA polymerase II change shapes to expose the template and unwind DNA.

The Transcription Unit

  • Composed of promoter, RNA coding sequence, and terminator.
  • The first transcribed nucleotide is +1.

Abortive Initiation

  • RNA polymerase is stalled and releases the short strands of RNA.
  • A 9-12 nucleotide long strand facilitates transition to elongation.
  • Transition occurs when transcript is ~30 nucleotides long enabling the polymerase to move downstream to continue transcription.

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Lecture 3 - Annotated - Gene Expression PDF

Description

This quiz delves into the key concepts of gene expression, including the roles of ribozymes, RNA polymerase, and the significance of enhancers and silencers. Test your knowledge on transcription processes and the differences between DNA and RNA. Ideal for students studying molecular biology or related fields.

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