Chapter 12 Flashcards
(39 cards)
What’s an operon
groups of functionally related structural genes and the sequences that control their transcription.
Whats negative control
a repressor protein binds to DNA and inhibits transcription
What’s positive control
an activator (regulatory protein) binds to DNA (usually at a site other than the operator) and stimulates transcription
What’s an inducible operon
transcription is normally off and must be turned on
What’s a repressible operon
repressible operons, transcription is normally on and must be turned off.
What kind of operon is the lac operon of E.coli and why
The lac operon of E. coli is a negative inducible operon. In the absence of lactose, a repressor binds to the operator and prevents the transcription of genes that encode β-galactosidase, permease, and transacetylase. When lactose is present, some of it is converted into allolactose, which binds to the repressor and makes it inactive, allowing the structural genes to be transcribed.
What kind of operon is the trp operon of E.coli
The trp operon of E. coli is a negative repressible operon that controls the biosynthesis of tryptophan.
In what ways do eukaryotic cells differ from bacteria in gene regulation
the absence of operons
the presence of chromatin
presence of a nuclear membrane.
How can chromatin structure be altered?
1) by chromatin-remodeling complexes that reposition nucleosomes
2) by modifications of histone proteins, including acetylation, phosphorylation, and methylation.
What control(s) the initiation of eukaryotic transcription and how
1) general transcription factors that assemble into the basal transcription apparatus
2) by transcriptional regulator proteins that stimulate or repress normal levels of transcription by binding to regulatory promoters and enhancers.
Enhancers affect the transcription of distant or proximal genes
distant genes
What are regulatory elements
DNA sequences that are not transcribed but play a role in regulating other nucleotide sequences
What are regulatory gene
encoding products that interact with other sequences and affect the transcription and translation of these sequences (DNA sequence–encoding products that affect the operon function but are not part of the operon)
Gene regulation’s role in bacteria
gene regulation maintains internal flexibility, turning genes on and off in response to environmental changes.
What’s a negative inducible operon
The control at the operator site is negative (repressor). Molecule is initially binding to the operator, inhibiting transcription. Such operons are usually off and need to be turned on, so the transcription is inducible.
What’s a corespressor
a small molecule that binds to the repressor and makes it capable of binding to the operator to turn off transcription
What’s a negative repressible operon
The control at the operator site is negative. But such transcription is usually on and needs to be turned off, so the transcription is repressible.
What’s the inducer of the lac operon
allolactose
T/F:repression of the lac operon
completely shuts down transcription
False: repression of the lac operon never
completely shuts down transcription.
What’s the role of insulators
Insulators limit the action of enhancers by blocking their action in a position-dependent manner.
T/F: Coordinately controlled genes in eukaryotic cells respond to the same factors because they have common response elements that are stimulated by the same transcriptional activator.
True
Name 4 elements important in controlling the stability of eukaryotic mRNAs.
1) 5’ cap
2) the poly(A) tail
3) the 5’ UTR, the coding region
4) sequences in the 3’ UTR
What do siRNA’s and miRNA’s do
These complexes cleave RNA, inhibit translation, affect RNA degradation, and silence transcription.
What makes Arabidopsis thaliana a good model organism
small and easy to maintain in lab , short generation time
