Podcast
Questions and Answers
What is the first step in gene expression?
What is the first step in gene expression?
- RNA processing
- Translation
- Replication
- Transcription (correct)
In which organisms does transcription-translation coupling occur?
In which organisms does transcription-translation coupling occur?
- Viruses
- Fungi
- Eukaryotes
- Prokaryotes (correct)
Which component is NOT a product of transcription?
Which component is NOT a product of transcription?
- DNA (correct)
- mRNA
- rRNA
- tRNA
What kind of sequence is found in eukaryotic genes?
What kind of sequence is found in eukaryotic genes?
What does hnRNA stand for?
What does hnRNA stand for?
What marks the start of transcription in a gene?
What marks the start of transcription in a gene?
Which step is NOT involved in the maturation of RNA?
Which step is NOT involved in the maturation of RNA?
What influences cellular function according to gene expression?
What influences cellular function according to gene expression?
What role do enhancers play in gene expression?
What role do enhancers play in gene expression?
Where does RNA synthesis occur?
Where does RNA synthesis occur?
Which of the following is a difference between RNA and DNA?
Which of the following is a difference between RNA and DNA?
What function do regulatory sequences in mRNA serve?
What function do regulatory sequences in mRNA serve?
What is the function of transcription starting site contained in the initiator?
What is the function of transcription starting site contained in the initiator?
How do enhancers and repressors affect gene expression?
How do enhancers and repressors affect gene expression?
What is the primary role of RNA polymerase?
What is the primary role of RNA polymerase?
In what format can enhancers or repressors affect gene expression?
In what format can enhancers or repressors affect gene expression?
Which RNA polymerase is primarily responsible for synthesizing mRNA?
Which RNA polymerase is primarily responsible for synthesizing mRNA?
What is the primary product of transcription referred to as?
What is the primary product of transcription referred to as?
What modification occurs immediately after the initiation of RNA synthesis?
What modification occurs immediately after the initiation of RNA synthesis?
What is the role of the polyadenylation signal in hnRNA processing?
What is the role of the polyadenylation signal in hnRNA processing?
What do exons represent in the context of pre-mRNA?
What do exons represent in the context of pre-mRNA?
Which of the following does NOT occur during the maturation of hnRNA?
Which of the following does NOT occur during the maturation of hnRNA?
What is the function of the 5’ cap added to mRNA?
What is the function of the 5’ cap added to mRNA?
Which enzyme is responsible for adding adenine nucleotides at the 3’ end of the hnRNA?
Which enzyme is responsible for adding adenine nucleotides at the 3’ end of the hnRNA?
What are the two main components of a gene producing mRNA?
What are the two main components of a gene producing mRNA?
What is the role of the basal promoter?
What is the role of the basal promoter?
Which of the following is an example of a proximal promoter element?
Which of the following is an example of a proximal promoter element?
Which direction does RNA polymerase read the DNA template?
Which direction does RNA polymerase read the DNA template?
What replaces thymine in the RNA sequence during transcription?
What replaces thymine in the RNA sequence during transcription?
The transcription start site is located where in relation to the promoter?
The transcription start site is located where in relation to the promoter?
What is the function of enhancers in gene regulation?
What is the function of enhancers in gene regulation?
Which protein complex is responsible for basal transcription in eukaryotes?
Which protein complex is responsible for basal transcription in eukaryotes?
Flashcards
Transcription
Transcription
The process of copying genetic information from DNA into RNA.
Central Dogma of Biology
Central Dogma of Biology
The central dogma describes the flow of genetic information from DNA to RNA to protein.
Transcription-Translation Coupling
Transcription-Translation Coupling
In prokaryotes (like bacteria), transcription and translation happen simultaneously. The mRNA is translated into a polypeptide even while it's being transcribed from DNA.
Introns
Introns
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Exons
Exons
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5' capping
5' capping
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Splicing
Splicing
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Polyadenylation
Polyadenylation
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Promoter
Promoter
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Promoter elements
Promoter elements
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TATA box
TATA box
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RNA polymerase
RNA polymerase
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Enhancer
Enhancer
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Template strand
Template strand
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Coding strand
Coding strand
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5' UTR
5' UTR
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Enhancer and Repressor Elements
Enhancer and Repressor Elements
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Initiator
Initiator
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hnRNA
hnRNA
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Termination Sequence
Termination Sequence
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Translation
Translation
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What does RNA polymerase I synthesize?
What does RNA polymerase I synthesize?
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What type of RNA is synthesized by RNA polymerase II?
What type of RNA is synthesized by RNA polymerase II?
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What is the role of RNA polymerase III?
What is the role of RNA polymerase III?
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What is the immediate product of transcription?
What is the immediate product of transcription?
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What are exons?
What are exons?
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What are introns?
What are introns?
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What is the 5' cap?
What is the 5' cap?
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What is the poly A tail?
What is the poly A tail?
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Study Notes
Transcription Overview
- Transcription is the first step in gene expression
- It's DNA-directed synthesis of RNA
- The process transforms a specific nucleotide sequence (genetic information) into a product influencing cellular function.
- RNA is either translated into protein (mRNA) or contributes to translation (rRNA, tRNA) or regulation (microRNA)
Central Dogma
- Replication (DNA→DNA): DNA polymerase
- Transcription (DNA→RNA): RNA polymerase
- Translation (RNA→Protein) Ribosome
Transcription Steps
- Initiation: RNA polymerase binds to promoter region, unwinds DNA
- Elongation: RNA polymerase moves along the template strand, synthesizing RNA in the 5' to 3' direction, using complementary base pairing.
- Termination: RNA polymerase reaches termination sequence, detaches from DNA, and releases newly synthesized RNA.
Gene Structure
- Gene: a minimal linear sequence of nucleotides encoding protein or structural RNA.
- Sequence is written 5' to 3'
- Eukaryotic genes: composed of exons (coding), introns (non-coding), and non-coding consensus (regulatory) sequences.
- Nucleotides before transcription start site have -ve numbers
- Nucleotides after start site have +ve numbers.
Gene Structure Components
- Coding region: transcribed into mRNA, translated into protein
- Regulatory region:
- Basal promoters: ensure basal expression, initiate transcription (example: TATA box)
- DNA regulatory elements: regulate gene expression (examples: proximal promoter elements, enhancers, repressors)
Promoter Elements
- Located upstream of transcription start site
- Crucial for binding RNA polymerase and initiation of transcription
- Examples include TATA box, CAAT box, and GC-rich regions
RNA Synthesis
- Occurs in the nucleus
- Catalyzed by RNA polymerase
- RNA polymerase uses DNA as a template
- RNA differs from DNA: single-stranded, uracil (U) instead of thymine (T), shorter length.
- Genes coding for proteins are transcribed into mRNA in the nucleus, translation in the cytosol
RNA Polymerases
- Multiple RNA polymerases in eukaryotes:
- RNA polymerase I (rRNA synthesis)
- RNA polymerase II (mRNA and microRNA synthesis)
- RNA polymerase III (tRNA and 5S rRNA synthesis)
- Transcription factors and accessory proteins (pre-initiation complex) essential for proper RNA polymerase positioning on DNA (upstream from start site)
Heterogeneous nuclear RNA (hnRNA)
- hnRNA (primary transcript), larger than mRNA in the cytoplasm
- Contains exons (coding) and introns (non-coding)
- Undergoes modifications to become mature mRNA
- Modifications include 5' cap addition, and Poly A tail addition, and intron removal.
5' cap
- Added after RNA initiation; a methyl guanosine residue via a 5' to 5' bridge
- Protects mRNA from degradation
- Aids mRNA binding to ribosomes for translation
Poly A tail
- AAUAAA sequence in the DNA( polyadenylation signal)
- Signal recognized by endonuclease, cuts RNA
- 250 adenine nucleotides added by Poly(rA) polymerase to the 3' end
- Important for mRNA stability and translation
Splicing
- Introns removed; exons joined to form mature mRNA
- Performed by small nuclear RNAs (snRNAs) and proteins (snRNPs) forming spliceosome.
- Mature mRNA passes through nuclear pores, translation in the cytoplasm
Splice Site Mutations
- Mutations at splice sites alter mRNA size/content
- Result in aberrant (abnormal) proteins
Summary Table
No longer relevant. Each bullet point is now an independent statement.
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Description
This quiz covers the essential processes of transcription in the context of the central dogma of molecular biology. You will explore the steps of transcription, the role of RNA polymerase, and the importance of gene structure. Ideal for students studying genetics or cell biology.
