Note
Studied by 25 people
Chapter 12: Gene Transcription and RNA Modification
Gene: A segment of DNA that contains the instructions for making a specific protein or set of proteins.
Transcription: The process of copying a segment of DNA into RNA.
Protein-coding genes: Genes that encode instructions for making proteins.
Translation: The process by which the sequence of an mRNA is converted into the sequence of amino acids in a protein.
Gene expression: The process by which information from a gene is used to synthesize a functional gene product (usually a protein).
Promoter: The DNA sequence where transcription begins.
Terminator: The DNA sequence where transcription ends.
Template Strand: The DNA strand that is copied into RNA.
Coding Strand: The DNA strand that has the same sequence as the RNA transcript (except T/U).
Proteins that bind to DNA and control the rate of transcription.
Can either facilitate or inhibit transcription.
Initiation: RNA polymerase binds to the promoter.
Elongation: RNA polymerase synthesizes RNA.
Termination: RNA synthesis ends, and the RNA molecule is released.
-35 and -10 Sequences: Key regions in bacterial promoters.
Pribnow Box: The -10 sequence.
RNA Polymerase Holoenzyme: Composed of the core enzyme and sigma factor.
Sigma Factor: Recognizes the promoter and initiates transcription.
RNA polymerase synthesizes RNA in the 5’ to 3’ direction.
The DNA double helix reforms behind the RNA polymerase.
Rho-dependent: Requires the rho protein.
Rho-independent: Involves a stem-loop structure and a uracil-rich sequence.
RNA pol I: Transcribes rRNA genes.
RNA pol II: Transcribes mRNA and some snRNA.
RNA pol III: Transcribes tRNA and some other small RNAs.
Contains the TATA box and the transcription start site.
Basal transcription occurs at low levels without additional regulatory elements.
Enhancers: DNA sequences that increase transcription rates.
Activators: Proteins that bind enhancers to increase transcription.
Repressors: Proteins that bind enhancers to decrease transcription.
Allosteric Model: RNA polymerase is destabilized and dissociates.
Torpedo Model: RNA polymerase is removed by an exonuclease.
TFIID: Binds to the TATA box in the core promoter.
TFIIA and TFIIB: Stabilize the binding of TFIID to the promoter.
TFIIF: Binds to RNA polymerase II and helps it bind to the promoter.
TFIIE and TFIIH: Bind to the complex, with TFIIH having helicase activity to unwind DNA and kinase activity to phosphorylate the CTD of RNA polymerase II.
Assembly of PIC: General transcription factors and RNA polymerase II assemble at the promoter.
DNA Unwinding: TFIIH unwinds the DNA at the transcription start site.
Formation of Open Complex: RNA polymerase II forms an open complex, allowing the template strand to be accessible.
Initiation of RNA Synthesis: RNA polymerase II begins synthesizing RNA from the DNA template.
Promoter Clearance: RNA polymerase II clears the promoter and enters the elongation phase.
Introns: Non-coding sequences removed from pre-mRNA.
Exons: Coding sequences that remain in mRNA.
Spliceosome: A complex that removes introns and joins exons.
Allows for different proteins to be produced from the same gene.
Addition of a 7-methylguanosine cap to the 5’ end of mRNA.
Important for mRNA stability and translation initiation.
Addition of a poly-A tail to the 3’ end of mRNA.
Enhances mRNA stability and export from the nucleus.
Modifications to the RNA sequence after transcription.
Can include base conversions and insertions/deletions.