33 Questions
What is the process of making an RNA copy of a gene sequence called?
Transcription
Which process involves translating the nucleotide sequence of an mRNA molecule to the amino acid sequence of a protein?
Translation
What does gene expression involve that requires intermediate molecules such as mRNA?
Indirect protein synthesis from DNA
What is the function of the carboxyl-terminal domain (CTD) phosphorylation of RNA Polymerase?
It releases the polymerase from the initiation complex
What is the role of basal transcription factors?
They are involved in transcription from all poly II promoters
What happens when the carboxy-terminal domain (CTD) of RNA Polymerase is phosphorylated?
Transcription begins
What is added to the 5’ end of the primary transcript of mRNA?
7-methylguanosin Cap structure
What is the function of splicing in mRNA processing?
Removal of introns
Where is the cap region found in eukaryotic mRNAs?
At the 5’ end
What is the main purpose of the poly-A tail added to the 3’ end of mRNA?
Stabilizes the mRNA and protects it from degradation
What does TF IIH helicase activity contribute to during transcription initiation?
Unwinding of 2 DNA strands
What is the function of the internal channel between the β and β' subunits of RNA polymerase?
Acts as the active site of the polymerase
What leads to the termination of transcription in E. coli?
Encounter with GC-rich inverted repeat followed by 7 adenine nucleotides
What makes eukaryotic transcription more complex compared to bacterial transcription?
All of the above
What is the role of TFII H in eukaryotic transcription?
Phosphorylates the C-terminus region of RNA Polymerase II
What is the function of RNA Polymerase II in eukaryotic mRNA synthesis?
Recognizes promoter regions
What are the components involved in the initiation of eukaryotic transcription?
TBP, TFIIB, TFIIE, TFIID, TFIIH
What is the role of TF-IIH in eukaryotic transcription initiation?
Helicase activity and protein kinase activity
What triggers chain termination during eukaryotic transcription?
Phosphorylation of C-terminus region of RNA Polymerase II
'Stabilization' refers to which aspect during mRNA synthesis?
Formation of stable stem-loop structure
What is required for bacterial genes termination signals?
GC-rich inverted repeat followed by 7 adenine nucleotides
What contributes to the complexity of eukaryotic transcription?
Presence of chromatin
During transcription, which enzyme is responsible for synthesizing mRNA in eukaryotic cells?
RNA Polymerase II
What is the function of the sigma (σ) subunit in prokaryotic RNA Polymerase?
Recognizing promoter sequences
Where are the consensus sequences TATA box and CAAT box located in the promoter regions of eukaryotic genes?
TATA box: -30 to -10 region; CAAT box: -150 to -70 region
What is the role of the pre-initiation complex during transcription initiation in eukaryotic cells?
Recruiting initiation factors
Which RNA Polymerase is responsible for the synthesis of tRNA in eukaryotic cells?
RNA Polymerase III
What occurs during transcription elongation?
Addition of nucleotides to the growing mRNA chain
Where does transcription take place in prokaryotic cells?
Cytoplasm
What happens during transcription termination?
Release of completed mRNA molecule
'Transcription factors can regulate gene expression by binding to specific DNA sequences' - Which stage of gene expression does this statement refer to?
Transcription
How can transcription errors influence gene expression?
Lead to synthesis of non-functional RNA or proteins
What can influence the process of transcription?
Temperature, pH, and nutrient availability
Study Notes
- Gene expression involves two main stages: Transcription and Translation
- Transcription is the first stage of gene expression, where DNA is copied into RNA
- RNA is synthesized through the action of RNA polymerases using ribonucleoside triphosphates and divalent metal ions
- mRNA, rRNA, tRNA, and small RNAs are synthesized during transcription
- Transcription in eukaryotic cells includes synthesis of RNA, processing/modifications, and requires specific promoter sequences
- RNA Polymerase was first discovered in E. coli and plays a crucial role in RNA synthesis
- Prokaryotic RNA Polymerase is a complex consisting of six polypeptides, with the sigma (σ) subunit recognizing promoter sequences
- Transcription is initiated by RNA polymerase binding to promoter sequences, unwinding DNA, and synthesizing a short RNA chain, which eventually leads to the separation of the σ subunit and the formation of a transcription bubble.
- In eukaryotic cells, RNA Polymerase II is responsible for the synthesis of mRNA, whereas RNA Polymerase I and III synthesize rRNA and tRNA, respectively.
- The promoter regions of eukaryotic genes contain the consensus sequences TATA box (-30 to -10 region) and CAAT box (-150 to -70 region), which help in the recruitment of RNA Polymerase and the initiation of transcription.
- The initiation of transcription in eukaryotic cells involves the binding of RNA Polymerase to the promoter regions, the melting and unwinding of the DNA double helix, and the formation of a pre-initiation complex.
- Once the pre-initiation complex is formed, the initiation factors are recruited, and the transcription bubble is formed, leading to the synthesis of the first few nucleotides of the mRNA.
- Transcription elongation involves the movement of RNA Polymerase along the DNA template, adding nucleotides to the growing mRNA chain, and unwinding and rewinding the DNA as necessary.
- Transcription termination occurs when RNA Polymerase reaches the termination sequence in the DNA, releasing the completed mRNA molecule and leaving the template DNA behind.
- The transcript produced during transcription undergoes various modifications, including capping, splicing, and polyadenylation, before it can be translated into a protein.
- RNA polymerase moves forward as it synthesizes the RNA chain, remaining associated with the template DNA during elongation.
- Transcription factors can regulate gene expression by binding to specific DNA sequences and modulating the activity of RNA Polymerase.
- Transcription can occur in the nucleus (eukaryotic cells) or in the cytoplasm (prokaryotic cells).
- Transcription errors can result in the production of non-functional RNA or proteins, which can lead to various diseases or developmental defects.
- Transcription can be influenced by various environmental factors, such as temperature, pH, and nutrient availability.
Test your knowledge on the elongation process in mRNA synthesis by RNA polymerase. Learn about the unwinding and rewinding of DNA, the active site of the polymerase, and the termination of RNA synthesis.
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