Gene Structure and Expression
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Questions and Answers

What differentiates eukaryotic genes from prokaryotic genes?

  • Eukaryotic genes are typically split by introns. (correct)
  • Eukaryotic genes are exclusively polycistronic.
  • Eukaryotic genes lack open reading frames.
  • Eukaryotic genes do not require transcription.

What is necessary for a eukaryotic gene transcript to be expressed?

  • The presence of exons alone.
  • Coupling of transcription and translation.
  • Removal of introns from the transcript. (correct)
  • The gene being located in the cytoplasm.

Which statement about prokaryotic gene expression is accurate?

  • Transcription and translation are uncoupled.
  • It occurs in the nucleus.
  • It often involves polycistronic mRNA. (correct)
  • Introns must be removed before translation.

What is the role of introns in eukaryotic genes?

<p>They separate exons within the gene. (B)</p> Signup and view all the answers

Which of the following best describes the central dogma of molecular biology?

<p>DNA is transcribed to RNA which is then transformed into proteins. (B)</p> Signup and view all the answers

What is the purpose of transporting eukaryotic mRNA out of the nucleus?

<p>To allow for translation into protein by ribosomes in the cytoplasm (B)</p> Signup and view all the answers

Which statement about eukaryotic mRNA processing is correct?

<p>Introns must be removed before translation can occur (C)</p> Signup and view all the answers

What feature is NOT typically found in eukaryotic gene structure?

<p>Multiple transcripts from a single mRNA molecule (A)</p> Signup and view all the answers

Which of the following correctly describes the TATA box in the core promoter?

<p>It is a conserved sequence found about -25 bases upstream of the transcription start site (D)</p> Signup and view all the answers

What role do proteins like cap-binding protein and poly-A-binding protein serve during mRNA export?

<p>They mark mRNA transcripts for export from the nucleus (C)</p> Signup and view all the answers

What is the correct sequence of events described by the central dogma of molecular biology?

<p>Transcription, Translation, Replication (C)</p> Signup and view all the answers

Which characteristic is true for gene expression in prokaryotes compared to eukaryotes?

<p>Prokaryotic genes are often organized in operons (A)</p> Signup and view all the answers

What is the primary function of intron removal in gene expression?

<p>To allow multiple proteins to be produced from a single gene (D)</p> Signup and view all the answers

What type of mRNA will be produced when an operon is transcribed in bacteria?

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

Why is the organization of genes in operons considered efficient for bacterial cells?

<p>It simplifies the necessity for multiple regulatory sequences (B)</p> Signup and view all the answers

What nucleotides are present in the RNA molecule during transcription?

<p>A, C, G, U (A)</p> Signup and view all the answers

What is likely the consequence of alternative splicing in eukaryotic gene expression?

<p>Production of multiple protein variants from a single gene (C)</p> Signup and view all the answers

Which of the following statements about DNA replication and transcription is true?

<p>Transcription uses the same template strand as replication (C)</p> Signup and view all the answers

What is the primary function of snRNA in the context of gene expression?

<p>Excises introns and joins exons (D)</p> Signup and view all the answers

How do promoter elements differ between simple single-celled eukaryotes and multicellular organisms?

<p>Regulatory elements may be located many kilobases away in multicellular organisms. (D)</p> Signup and view all the answers

What is the result of alternative splicing in eukaryotic genes?

<p>Multiple proteins with different functions from a single gene. (B)</p> Signup and view all the answers

Which molecules are primarily involved in the excising of introns in eukaryotes?

<p>Small nuclear RNA and proteins (C)</p> Signup and view all the answers

Transcription of all eukaryotic protein-coding genes involves which of the following?

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

In the context of gene expression, which aspect of multicellular organisms is highlighted?

<p>They can have multiple regulatory elements affecting the same gene. (A)</p> Signup and view all the answers

Which of the following statements about introns and exons is true?

<p>Exons are spliced together to form the mature transcript. (B)</p> Signup and view all the answers

What is a key feature of ribosomal gene transcription in eukaryotes?

<p>It synthesizes various small RNAs including rRNA and tRNA. (D)</p> Signup and view all the answers

What is the main protein mentioned that is to be cloned and expressed in E.coli?

<p>Myeloid Leukaemia Factor 1 (B)</p> Signup and view all the answers

Which method is necessary to avoid issues with splicing when preparing for polymerase chain reaction?

<p>Using cDNA (A)</p> Signup and view all the answers

What type of information can be accessed through ENSEMBL regarding genes?

<p>Positions and structures of genes (B)</p> Signup and view all the answers

Why is it not possible to use genomic DNA for the specific aims outlined?

<p>It includes introns that complicate processing (D)</p> Signup and view all the answers

What is the primary goal of the practical exercise mentioned for Week 2?

<p>To amplify, clone, sequence, and express MLF1 (B)</p> Signup and view all the answers

Flashcards

mRNA (Messenger RNA)

A single-stranded molecule that carries genetic information from DNA to ribosomes for protein synthesis.

Transcription

The process of creating a copy of a gene from DNA into RNA.

Translation

The process of translating the genetic code in mRNA into a sequence of amino acids to build a protein.

Operon

A group of genes that are transcribed together as a single unit in bacteria, often involved in the same metabolic pathway.

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Polycistronic mRNA

A single mRNA molecule that carries the code for multiple genes.

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Gene Regulation

The regulation of gene expression, determining which genes are transcribed and translated.

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Intron Removal

The removal of non-coding sequences (introns) from pre-mRNA, producing mature mRNA.

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Alternative Splicing

The process of splicing pre-mRNA in different ways to produce multiple protein isoforms from a single gene.

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Open Reading Frame (ORF)

The section of a gene that codes for a protein, composed of exons.

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Introns

Non-coding DNA sequences within a gene that are removed during mRNA processing.

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Intron Removal (Splicing)

The process of removing introns from pre-mRNA to create mature mRNA.

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Coupled Transcription and Translation

The process of transcribing and translating DNA into protein, occurring simultaneously in prokaryotes.

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mRNA

A type of RNA that carries genetic information from DNA to ribosomes, where protein synthesis occurs.

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RNAP in snRNA genes

Specific RNA polymerase (RNAP) that is responsible for transcribing only snRNA genes, which are essential for splicing.

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Upstream Promoter Elements

The upstream regulatory sequences located before the core promoter, influencing gene expression.

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Transcription of ribosomal genes

The process of synthesizing ribosomal RNA (rRNA), transfer RNA (tRNA), and other small RNAs.

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Transcription of eukaryotic protein-coding genes

The process of transcribing all eukaryotic protein-coding genes.

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RNAP III transcription

The process of transcribing DNA to synthesize ribosomal 5S rRNA, tRNA, and other small RNAs.

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Promoter Complexity

The complexity of promoters in different organisms.

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Study Notes

Gene Structure and Expression

  • Genes in eukaryotes are more complex than in prokaryotes.
  • Eukaryotic genes are composed of exons (coding regions) and introns (non-coding regions).
  • Introns must be removed from primary transcripts to produce mature mRNA before translation
  • Prokaryotic genes are often arranged in operons, allowing multiple genes to be transcribed together into a single polycistronic mRNA.
  • This is efficient for prokaryotes since all genes involved in synthesizing a particular molecule can all be synthesized together.
  • Eukaryotic gene expression is uncoupled, requiring mRNA processing and transport to the cytoplasm before translation.
  • Eukaryotic mRNAs are modified (capped and polyadenylated) for stability and to aid transport from the nucleus.
  • Eukaryotic mRNA transcripts are monocistronic, translating only one gene at a time.
  • Prokaryotic organisms do not have a nucleus so transcription and translation occur simultaneously within the cytoplasm.

Central Dogma

  • The central dogma describes the flow of genetic information, from DNA to RNA to protein.
  • DNA is transcribed into RNA, and RNA is translated into protein.
  • DNA replication copies DNA to ensure that genetic information can be passed on to new cells.
  • In prokaryotes, this process occurs in the cytoplasm.
  • In eukaryotes, transcription occurs in the nucleus, and the resulting mRNA is then exported to the cytoplasm for translation.

Eukaryotic mRNA Processing

  • Eukaryotic pre-mRNA undergoes processing steps to become mature mRNA.
  • Processing steps include splicing, 5' capping, and 3' polyadenylation.
  • Splicing removes introns from the pre-mRNA.
  • The 5' cap is added to the beginning of the mRNA.
  • The 3' poly(A) tail is added to the end of the mRNA.
  • mRNA export to cytoplasm needs to occur before translation.

Alternative Splicing

  • Alternative splicing produces different proteins from a single gene, enabling multiple proteins with different functions to arise from a single gene.
  • This involves different combinations of exons from a gene being joined together to form different mature mRNA transcripts, which will ultimately translate to different proteins

Core Promoter Elements

  • Core promoters are conserved sequences in eukaryotes.
  • They help recruit RNA polymerase to initiate transcription.
  • Examples of these sequences include the TATA box, Initiator (Inr), Downstream Promoter Element (DPE), and GC box.

Upstream Promoter Elements

  • Upstream promoter elements are sequences further upstream of the core promoter.
  • They enhance or suppress gene transcription by interacting with other proteins and with RNA polymerase.
  • These elements are more complex in eukaryotes compared to prokaryotes.

Practical Implications

  • Learning outcomes included understanding transcription and translation in prokaryotes and eukaryotes, and how this relates to practical applications such as cloning.
  • The aim of a given practical may involve amplifying, cloning, sequencing, and expressing a specific protein (e.g., MLF1) in E. coli.

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Structure of Genes 2024 PDF

Description

This quiz explores the differences in gene structure and expression between eukaryotes and prokaryotes. It covers key concepts such as the composition of genes, mRNA processing, and the transcription-translation processes. Test your understanding of how eukaryotic genes are more complex and the implications for gene expression.

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