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.
