Unit3 - Part 3 Flashcards
trp attenuation
A regulatory mechanism in bacteria that controls the expression of genes involved in tryptophan biosynthesis. It involves premature termination of transcription.
attenuator
A DNA sequence within the leader region of an operon that can form alternative stem-loop structures, affecting transcription termination.
tryptophan
An amino acid that serves as a corepressor in the trp operon.
repressor
A protein that binds to an operator sequence, inhibiting transcription.
2:3 stem loop forms
A stem-loop structure that forms in the leader mRNA when tryptophan levels are high, leading to transcription termination.
poly U
A stretch of uracil nucleotides in the leader mRNA that follows the 2:3 stem loop, contributing to the stability of the termination structure.
What dictates which stem loops form?
The availability of tryptophan-charged tRNAs and the rate of ribosome movement along the leader mRNA.
trp-charged tRNAs
When tryptophan levels are high, there are more trp-charged tRNAs available, which allows the ribosome to move quickly through the leader region, promoting the formation of the 2:3 stem loop and transcription termination.
RNA polymerase
The enzyme that synthesizes RNA from a DNA template.
inducible
A gene or operon whose expression is increased in response to a specific stimulus.
open reading frame (ORF)
A sequence of DNA or RNA that can be translated into a protein.
monocistronic
Describing mRNA that encodes a single protein.
polycistronic
Describing mRNA that encodes multiple proteins.
operon operator
A DNA sequence within the operon that binds to a repressor protein, inhibiting transcription.
repressor
A protein that binds to an operator sequence, inhibiting transcription.
inducer
A molecule that binds to a repressor protein, causing it to release from the operator and allowing transcription to proceed.
constitutive gene expression
The continuous expression of a gene or operon.
beta-galactosidase
An enzyme that breaks down lactose into glucose and galactose.
permease
A protein that transports lactose into the cell.
transacetylase
An enzyme involved in the metabolism of lactose.
operator
A DNA sequence within the operon that binds to a repressor protein, inhibiting transcription.
cAMP
Cyclic adenosine monophosphate, a second messenger molecule that activates the CAP protein.
CAP site
A DNA sequence within the promoter region of the lac operon that binds to the CAP-cAMP complex, enhancing transcription.
How does the presence of glucose regulate the lac operon?
Glucose inhibits the production of cAMP, which reduces the activity of the CAP-cAMP complex. This leads to decreased transcription of the lac operon.
core enzyme
The portion of RNA polymerase that catalyzes RNA synthesis.
holoenzyme
The complete RNA polymerase enzyme, consisting of the core enzyme and a sigma factor.
sigma factor
A protein that helps RNA polymerase recognize the promoter sequence and initiate transcription.
transcription factor
A protein that binds to DNA and regulates gene expression.
terminator
A DNA sequence that signals the end of transcription.
promoter
A DNA sequence that signals the start of transcription.
What components are necessary for transcription to end?
A terminator sequence in the DNA and specific RNA sequences that form a hairpin structure.
