BIOL 3301 EXAM QUESTIONS AND ANSWERS
LATEST UPDATE (GRADED A+)
Transcription occurs in three stages:
Initiation
Elongation
Termination
These steps involve protein-DNA interactions
- Proteins such as RNA polymerase interact with DNA sequences
Structural genes and RNA transcripts
- Transcribed into mRNA
- Constitutes about 90% of all genes
Non-structural genes and RNA transcripts
Not translated but transcribed
- Ribosomes
- Spliceosomes
- Signal Recognition Particle
- Telomerase
In E.coli the RNA polymerase holoenzyme is composed of:
Core enzyme - Five subunits
α2ββ'ω
Sigma factor - One subunit
σ
These subunits play distinct functional roles
How does the initiation of transcription in bacteria happen?
RNA polymerase holoenzyme binds loosely to the the DNA, then scans along the DNA until it encounters
a promoter region. Binding of RNA polymerase to promoter forms the closed complex. The sigma factor
recognizes both the -35 and -10 regions. The open complex is formed when the TATAAT box in the -10
region is unwound.
- A-T bonds are more easily separated
A short RNA strand is made within the open complex
- The sigma factor is released at this point, which marks the end of initiation
, How does the elongation phase of bacteria begin?
After initiation, the core enzyme slides down the DNA to synthesize an RNA strand. The open complex
formed by the action of RNA polymerase is about 17 bases long. Behind the open complex, the DNA
rewinds back into a double helix.
How does the termination of bacterial transcription happen?
E. coli has two different mechanisms for termination:
1. rho-dependent termination
- requires a protein known as Ρ (rho)
2. rho-independent termination
RNA pol I
Transcribes all rRNA genes (except for the 5S rRNA)
RNA pol II
-transcribes all protein-encoding (structural) genes, thus synthesizes all mRNAs
-transcribes some snRNA genes needed for splicing
RNA pol III
- transcribes all tRNA genes
- And the 5S rRNA gene
- microRNA genes
What is the core promoter?
relatively short DNA sequence that is necessary for transcription to take place
- Consists of the TATA box and transcriptional start site
- Important in determining the precise start point for transcription
Basal transcription
Low level of transcription
What are regulatory elements?
short DNA sequences that affect the binding of RNA polymerase to the promoter
Transcription factors (proteins)
Bind to regulatory elements and influence the rate of transcription
What are two types of regulatory elements?
- enhancers (stimulate transcription) and silencers (inhibit transcription)
- they vary widely in their locations but are often found in the -50 to -100 region
Factors that control gene expression can be divided into what two types?
LATEST UPDATE (GRADED A+)
Transcription occurs in three stages:
Initiation
Elongation
Termination
These steps involve protein-DNA interactions
- Proteins such as RNA polymerase interact with DNA sequences
Structural genes and RNA transcripts
- Transcribed into mRNA
- Constitutes about 90% of all genes
Non-structural genes and RNA transcripts
Not translated but transcribed
- Ribosomes
- Spliceosomes
- Signal Recognition Particle
- Telomerase
In E.coli the RNA polymerase holoenzyme is composed of:
Core enzyme - Five subunits
α2ββ'ω
Sigma factor - One subunit
σ
These subunits play distinct functional roles
How does the initiation of transcription in bacteria happen?
RNA polymerase holoenzyme binds loosely to the the DNA, then scans along the DNA until it encounters
a promoter region. Binding of RNA polymerase to promoter forms the closed complex. The sigma factor
recognizes both the -35 and -10 regions. The open complex is formed when the TATAAT box in the -10
region is unwound.
- A-T bonds are more easily separated
A short RNA strand is made within the open complex
- The sigma factor is released at this point, which marks the end of initiation
, How does the elongation phase of bacteria begin?
After initiation, the core enzyme slides down the DNA to synthesize an RNA strand. The open complex
formed by the action of RNA polymerase is about 17 bases long. Behind the open complex, the DNA
rewinds back into a double helix.
How does the termination of bacterial transcription happen?
E. coli has two different mechanisms for termination:
1. rho-dependent termination
- requires a protein known as Ρ (rho)
2. rho-independent termination
RNA pol I
Transcribes all rRNA genes (except for the 5S rRNA)
RNA pol II
-transcribes all protein-encoding (structural) genes, thus synthesizes all mRNAs
-transcribes some snRNA genes needed for splicing
RNA pol III
- transcribes all tRNA genes
- And the 5S rRNA gene
- microRNA genes
What is the core promoter?
relatively short DNA sequence that is necessary for transcription to take place
- Consists of the TATA box and transcriptional start site
- Important in determining the precise start point for transcription
Basal transcription
Low level of transcription
What are regulatory elements?
short DNA sequences that affect the binding of RNA polymerase to the promoter
Transcription factors (proteins)
Bind to regulatory elements and influence the rate of transcription
What are two types of regulatory elements?
- enhancers (stimulate transcription) and silencers (inhibit transcription)
- they vary widely in their locations but are often found in the -50 to -100 region
Factors that control gene expression can be divided into what two types?
