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Questions and Answers
What is the primary function of the σ subunit in RNA polymerase?
What is the primary function of the σ subunit in RNA polymerase?
Which type of sigma factor is essential for the transcription of housekeeping genes?
Which type of sigma factor is essential for the transcription of housekeeping genes?
What is the mechanism of intrinsic termination in bacteria?
What is the mechanism of intrinsic termination in bacteria?
What is the function of Rho protein in transcriptional termination?
What is the function of Rho protein in transcriptional termination?
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What is the core enzyme of RNA polymerase composed of?
What is the core enzyme of RNA polymerase composed of?
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What is the primary role of transcriptional termination in bacteria?
What is the primary role of transcriptional termination in bacteria?
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What is the definition of an insertion mutation?
What is the definition of an insertion mutation?
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What is a possible consequence of an insertion mutation?
What is a possible consequence of an insertion mutation?
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What is the result of a three-nucleotide insertion in the CFTR gene?
What is the result of a three-nucleotide insertion in the CFTR gene?
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What is an example of a disease caused by an insertion mutation?
What is an example of a disease caused by an insertion mutation?
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What is the effect of an insertion mutation on the reading frame of the genetic code?
What is the effect of an insertion mutation on the reading frame of the genetic code?
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Study Notes
Transcription in Bacteria
RNA Polymerase
- The primary enzyme responsible for transcribing DNA into RNA in bacteria
- Consists of 5 subunits: α2, β, β', ω, and σ (sigma factor)
- The σ subunit is responsible for recognizing and binding to specific DNA sequences
- The core enzyme (α2, β, β', ω) is responsible for the transcription process
Sigma Factors
- A family of proteins that bind to the RNA polymerase core enzyme, allowing it to recognize and bind to specific DNA sequences
- Different sigma factors recognize different promoter sequences, allowing for the regulation of gene expression
- The most common sigma factor in E. coli is σ70 (RpoD)
- Sigma factors can be classified into two groups:
- Primary sigma factors: essential for transcription and recognition of housekeeping genes
- Alternative sigma factors: regulate transcription of specific genes in response to environmental stimuli
Transcriptional Termination
- The process by which transcription is stopped and the RNA polymerase is released from the DNA template
- There are two main mechanisms of transcriptional termination in bacteria:
- Intrinsic termination: uses a terminator sequence that forms a hairpin loop, causing the RNA polymerase to pause and release the transcript
- Rho-dependent termination: uses the Rho protein to bind to the transcript and pull it away from the RNA polymerase, causing termination
- Transcriptional termination is an important mechanism for regulating gene expression and preventing the transcription of unwanted genes
Transcription in Bacteria
RNA Polymerase
- Primary enzyme responsible for transcribing DNA into RNA in bacteria
- Comprised of 5 subunits: α2, β, β', ω, and σ (sigma factor)
- σ subunit recognizes and binds to specific DNA sequences
- Core enzyme (α2, β, β', ω) carries out the transcription process
Sigma Factors
- Family of proteins that bind to RNA polymerase core enzyme, enabling recognition of specific DNA sequences
- Different sigma factors recognize distinct promoter sequences, regulating gene expression
- σ70 (RpoD) is the most common sigma factor in E. coli
- Classified into two groups:
- Primary sigma factors: essential for transcription and recognition of housekeeping genes
- Alternative sigma factors: regulate transcription of specific genes in response to environmental stimuli
Transcriptional Termination
- Process by which transcription is stopped and RNA polymerase is released from DNA template
- Two main mechanisms:
- Intrinsic termination: uses terminator sequence that forms a hairpin loop, causing RNA polymerase to pause and release transcript
- Rho-dependent termination: uses Rho protein to bind to transcript, pulling it away from RNA polymerase, causing termination
- Transcriptional termination crucial for regulating gene expression and preventing transcription of unwanted genes
Mutation Types
Insertion Mutation
- An insertion mutation occurs when one or more nucleotides are added to a DNA sequence.
- This type of mutation can alter the reading frame of the genetic code, resulting in a non-functional or abnormal protein.
- The consequences of an insertion mutation include:
- Frameshift mutation, where the reading frame is shifted, leading to a completely different amino acid sequence.
- Premature stop codon, where the insertion introduces a premature stop codon, resulting in a truncated protein.
- Altered gene expression, where the insertion affects the regulation of gene expression, leading to changes in protein production.
- Examples of insertion mutations include:
- Sickle cell anemia, where a single nucleotide insertion in the HBB gene leads to a frameshift mutation, resulting in abnormal hemoglobin production.
- Cystic fibrosis, where a three-nucleotide insertion in the CFTR gene leads to a premature stop codon, resulting in a non-functional protein.
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Description
Understand the process of transcription in bacteria, including the role of RNA polymerase and sigma factors in recognizing and binding to DNA sequences.
