Podcast
Questions and Answers
What is the role of aminoacyl AMP in the formation of aminoacyl tRNA?
What is the role of aminoacyl AMP in the formation of aminoacyl tRNA?
Which component primarily constitutes the structural scaffold of ribosomal RNA in E.coli?
Which component primarily constitutes the structural scaffold of ribosomal RNA in E.coli?
Which of the following statements accurately describes ribosome composition?
Which of the following statements accurately describes ribosome composition?
What are the three binding sites for tRNA found in a ribosome?
What are the three binding sites for tRNA found in a ribosome?
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What is not a function associated with the ribosome?
What is not a function associated with the ribosome?
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What is the role of TFIID in transcription initiation?
What is the role of TFIID in transcription initiation?
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What does the Mediator protein do in the pre-initiation complex?
What does the Mediator protein do in the pre-initiation complex?
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Which factors are included in the pre-initiation complex alongside RNA polymerase?
Which factors are included in the pre-initiation complex alongside RNA polymerase?
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What happens when the C-terminal domain of RNA polymerase is phosphorylated?
What happens when the C-terminal domain of RNA polymerase is phosphorylated?
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Which of the following is not a transcription factor involved in the pre-initiation complex?
Which of the following is not a transcription factor involved in the pre-initiation complex?
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What is the primary function of the poly-A tail in mRNA processing?
What is the primary function of the poly-A tail in mRNA processing?
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What components are involved in the formation of the spliceosome complex?
What components are involved in the formation of the spliceosome complex?
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What is the initial step in the splicing process of pre-mRNA?
What is the initial step in the splicing process of pre-mRNA?
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What role do ribozymes play in mRNA splicing?
What role do ribozymes play in mRNA splicing?
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How many protein molecules typically make up the small nuclear ribonuclear particles (snRNPs) involved in splicing?
How many protein molecules typically make up the small nuclear ribonuclear particles (snRNPs) involved in splicing?
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What is the primary difference in the processing of mRNA between prokaryotes and eukaryotes?
What is the primary difference in the processing of mRNA between prokaryotes and eukaryotes?
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Which stage is NOT part of the post-transcriptional processing of eukaryotic mRNA?
Which stage is NOT part of the post-transcriptional processing of eukaryotic mRNA?
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What modification occurs at the 5' end of eukaryotic pre-mRNA?
What modification occurs at the 5' end of eukaryotic pre-mRNA?
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What structural feature is unique to eukaryotic mRNA compared to prokaryotic mRNA?
What structural feature is unique to eukaryotic mRNA compared to prokaryotic mRNA?
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In eukaryotic mRNA processing, what is the function of the 3’ poly A tail?
In eukaryotic mRNA processing, what is the function of the 3’ poly A tail?
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What is the role of aminoacyl tRNA synthetases in the process of translation?
What is the role of aminoacyl tRNA synthetases in the process of translation?
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What is the typical length of tRNA molecules?
What is the typical length of tRNA molecules?
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Which of the following statements best describes the structure of tRNA?
Which of the following statements best describes the structure of tRNA?
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What occurs during the cleavage at the 3’ splice site?
What occurs during the cleavage at the 3’ splice site?
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How does an amino acid become linked to tRNA?
How does an amino acid become linked to tRNA?
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What is the purpose of the 5' cap added to mRNA?
What is the purpose of the 5' cap added to mRNA?
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How is the 5' cap added to the mRNA molecule?
How is the 5' cap added to the mRNA molecule?
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What sequence is essential for the polyadenylation of mRNA?
What sequence is essential for the polyadenylation of mRNA?
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What is typically cleaved by endonuclease during polyadenylation?
What is typically cleaved by endonuclease during polyadenylation?
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What modification is made to the G added during 5' capping of mRNA?
What modification is made to the G added during 5' capping of mRNA?
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Which of the following components indicates the necessity for polyadenylation?
Which of the following components indicates the necessity for polyadenylation?
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What feature of the AAUAAA sequence is crucial for its function in mRNA processing?
What feature of the AAUAAA sequence is crucial for its function in mRNA processing?
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Which of the following correctly describes the structure of the 5' cap on mRNA?
Which of the following correctly describes the structure of the 5' cap on mRNA?
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What role do methyl groups play in mRNA processing?
What role do methyl groups play in mRNA processing?
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What is the typical distance from the AAUAAA sequence where endonuclease cleaves the pre-mRNA?
What is the typical distance from the AAUAAA sequence where endonuclease cleaves the pre-mRNA?
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Study Notes
Gene Expression and Regulation
- Gene expression involves transcription, mRNA processing, and translation
- Prokaryotes and eukaryotes differ in how they regulate gene expression
- Gene expression is the process of using a gene's information to make a product (like protein or RNA)
Prokaryotic Transcription
- DNA-dependent RNA polymerases (also called RNA polymerases) incorporate nucleotides into RNA from a DNA template
- Bacterial RNA polymerase comprises six subunits: two α, one β, one β', one ω, and one σ
- The σ subunit is weakly bound and can dissociate.
- Transcription begins at a promoter (upstream), and halts at a terminator (downstream)
- Prokaryotic promoters have conserved sequences, such as the -35 and -10 sequence elements ("Pribnow box")
- The sigma subunit binds to consensus sequences within the -35 and -10 regions
Eukaryotic Transcription
- Eukaryotes have three RNA polymerases (I, II, and III), each directing the transcription of specific RNA types.
- RNA polymerase II transcribes mRNA and requires a pre-initiation complex, comprising multiple transcription factors and protein-DNA interactions
- RNA polymerase II preinitiation complex begins with the binding of TFIID to BRE, TATAA, etc consensus sequences via protein-DNA interactions
- Subsequent phases involve the addition of other transcription factors and the mediator complex and then RNA polymerase II.
mRNA Processing
- Prokaryotes have simultaneous transcription-translation in a single compartment, without mRNA processing
- Eukaryotes have mRNA processing before translation, involving three stages:
- 5' capping: Addition of a modified guanine nucleotide to the 5' end.
- 3' polyadenylation: Addition of a poly-A tail (adenine nucleotides) to the 3' end.
- Splicing: Removal of non-coding introns and joining of exons.
Transcription Termination in Prokaryotes
- Termination can be signaled by a G-C rich inverted repeat followed by 7A residues.
- This forms a stable stem-loop structure to terminate transcription and allow mRNA to dissociate from the DNA template
- Alternatively, a termination protein (Rho) can terminate transcription.
Ribosomes
- Ribosomes are molecular machines interpreting mRNA code
- Prokaryotic ribosomes are 70S, consisting of 50S and 30S subunits.
- Eukaryotic ribosomes are 80S, consisting of 60S and 40S subunits
- Ribosomes have RNA and proteins.
- Ribosomes have binding sites for mRNA and tRNA.
Translation
- Translation is the process from mRNA to protein.
- The process requires aminoacyl tRNA, ribosomes, mRNA, and initiation and elongation factors.
- The code is interpreted by the ribosome using tRNA.
- Transfer RNAs (tRNAs) are attached to amino acids.
- Aminoacyl tRNA synthetases catalyze the linkage of amino acids to tRNAs.
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Description
This quiz covers the vital concepts of gene expression and its regulation in both prokaryotes and eukaryotes. Learn about transcription mechanisms, the role of RNA polymerases, and key promoter sequences necessary for gene activation. Test your understanding of how different organisms control gene expression.
