Week 10 - Transcription Flashcards
Initiation
The beginning of transcription, where RNA polymerase binds to DNA at the promoter region (often near the TATA box) and starts RNA synthesis.
Elongation
RNA polymerase moves along the DNA template strand, adding RNA nucleotides in the 5’ to 3’ direction.
Termination
RNA polymerase stops transcription when it reaches a termination signal; the RNA transcript is released.
Processing
Post-transcriptional modifications of pre-mRNA: includes 5’ capping, 3’ polyadenylation, and splicing.
Transcription Start Site (TSS)
The location on the DNA where transcription begins (usually a purine base).
Transcription Termination Site (TTS)
The location on DNA where transcription ends.
Direction of RNA Synthesis
RNA is synthesized in the 5′ to 3′ direction, using the 3′ to 5′ DNA template strand.
RNA Polymerase II
Transcribes mRNA and some snRNA.
RNA Polymerase I
Transcribes rRNA (except 5S rRNA).
RNA Polymerase III
Transcribes tRNA, 5S rRNA, and other small RNAs.
Template Strand
The DNA strand used as a template to synthesize RNA.
Nontemplate (Coding) Strand
The DNA strand not used in transcription; its sequence matches the RNA (except T = U in RNA).
TATA Box
A DNA sequence in the promoter that helps position RNA polymerase at the TSS.
Enhancer
DNA sequences that can increase transcription from a distance via interaction with activator proteins.
General Transcription Factors (GTFs)
Proteins required for transcription initiation by RNA polymerase II, including TFIID, TFIIH, and mediator proteins.
Mediator Proteins
Act as a bridge between transcription factors and RNA polymerase II to initiate transcription.
Specific Transcription Factors
Bind to enhancers or silencers to regulate gene expression in a cell- or signal-specific manner.
5′ UTR (Untranslated Region)
The sequence upstream of the start codon; not translated into protein.
3′ UTR
The sequence downstream of the stop codon; affects mRNA stability, localization, and translation efficiency.
Exon
A coding region of a gene that remains in mRNA after splicing.
Intron
A noncoding region removed during splicing.
5’ Cap
A modified guanine nucleotide added to the 5’ end of mRNA for stability and ribosome binding.
3′ Poly(A) Tail
A stretch of adenines added to the 3’ end of mRNA to protect from degradation and aid in export.
PolyA Polymerase
Adds the poly(A) tail to the pre-mRNA’s 3′ end.
Primary Transcript (pre-mRNA)
The initial RNA transcript before processing.
Mature mRNA
Processed mRNA that includes exons, 5′ cap, and poly(A) tail, ready for translation.
Spliceosome
A large complex of proteins and snRNAs that removes introns from pre-mRNA.
Splicing (Order & Lariat)
- 5′ splice site is cut
- The intron loops into a lariat structure
- 3′ splice site is cut, and exons are joined
Alternative Splicing
Different combinations of exons are joined to create multiple proteins from one gene; adds diversity.
Start of Translation
Begins at the start codon (AUG), which codes for methionine.
End of Translation
Ends at a stop codon (UAA, UAG, or UGA), triggering release of the polypeptide.
RNA Translation Initiation
Begins with ribosome assembly at the start codon on the mRNA, guided by initiation factors.
RNA Nuclear Export
Processed mRNA is exported from the nucleus to the cytoplasm via nuclear pores.
RNA Stability
Refers to how long mRNA remains intact in the cell; influenced by the 5′ cap, 3′ UTR, poly(A) tail, and RNA-binding proteins.
Prokaryotic RNA Polymerase
A single RNA polymerase transcribes all types of RNA (mRNA, rRNA, tRNA).
Sigma Factors
Proteins that guide prokaryotic RNA polymerase to specific promoters.
Intronless
Most prokaryotic genes lack introns.
Cotranscriptional Translation
In prokaryotes, translation begins on the mRNA while it’s still being transcribed—because there’s no nucleus.
Polycistronic RNA
An mRNA molecule that encodes multiple proteins, common in prokaryotes.
