Bacterial Replication and Transcription 5.2 Flashcards
Transcription is the synthesis of? Requires?
RNA from DNA template
* requires the enzyme RNA polymerase
and a DNA template
What are the three major types of RNA that are synthesized?
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribosomal RNA (rRNA)
Is a primer required to initiate RNA synthesis?
no
Is a promoter required to initiate RNA synthesis?
yes
Transcription is the sequential addition of nucleotide bases onto the ___ ends of growing chains
3’
RNA polymerase recognition of promoter requires a?
sigma factor protein
what is a sigma factor protein?
a DNA binding protein that recognizes nucleotide sequences of promoters
What is needed for RNA polymerase to bind at the correct transcription start site?
recognition sequences
Where are two highly conserved regions needed for recognition and transcription?
~10 and ~35 bases upstream from where RNA synthesis begins
Termination of RNA synthesis is dependent upon?
the recognition of specific base sequences by the polymerase at a stem-loop structure in RNA
Does a unit of transcription contain one or many genes? Explain this significance
more than one
- Transcription of several genes into a single mRNA molecule usually occurs in prokaryotes
- THEREFORE the mRNA may contain the information for more than one polypeptide= polycistronic message
what is a polycistronic message?
1) has multiple translation start and stop sites
2) contains info for more than one polypeptide
3) common in bacterial and chloroplast mRNAs
What 3 location can control of gene expression or product activity occur?
1) transcriptional level
2) transnational level
3) post transnational level
Regulation at the transcriptional level is achieved by what 7 things?operos
- Induction (coming into existance)
- Repression (stopped from coming into existance)
- Positive control
- Global control/catabolite repression
- Quorum sensing
- Attenuation (translational control)
- Two component signal transduction (cell signalling method)
What gives transcriptional control at a promoter region?
certain proteins have to bind to DNA
*this occurs due to interactions between specific domains of the proteins and specific regions or motifs of the DNA molecule
helix-turn-helix motif protein
DNA binding protein
*one helix binds to one strand, the 2nd helix to the other strand; allows for binding of nucrleotide sequences
zinc finger motif
DNA binding protein
*a protein that binds a zinc ion as the protein’s zinc finger binds to DNA
What is an operon?
regulatory region plus coding region
*Genes that are transcribed together from a single promoter
In prokaryotes, genes involved in similar metabolic pathways are often linked to the same?
promoter to yield a polycistronic messenger RNA
All genes linked to some promoter can be _____ or _____ simultaneously?
downregulated (repression) or upregulated (induction) simultaneously
Repression occurs when?
a repressor protein binds to operator region of an operon
Promoter region-site where _____ binds
RNA polymerase
Repressor binds to ______ to prevent transcription
operator DNA
How is the repressor capable of binding to an operator?
by a corepressor binding to thee repressor
repressors contain _____ sites which the corepressor can bind to
allosteric sitres
the corepressor is often an end product from an?
anabolic pathway
What increases the affinity for operator DNA and a repressor?
the binding of a corepressor to the repressor
What is the ultimate complex that prevents RNA polymerase from transcribing genes?
repressor/corepressor/operator complex
What decreases the affinity for operator DNA and a repressor?
an inducer binding to repressor at allosteric site changes conformation of repressor decreasing its affinity for operator DNA
In case of Lactose operon, what is the inducer? derived from?
allolactose
*derived from lactose (via beta-galactosidase) that needs to be catabolized by the bacterial cell
