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21 Cards in this Set

  • Front
  • Back
operon
-group of genes that functions as units.
-3 types of genes
structural genes
in operon that code for enzymes in a metabolic pathwy.
operator gene
determines whether the structural genes will be transcribed or not.
promoter gene
the location where RNA polymerase binds to begin the process of transcription
repressor gene
codes for the production of a repressor protein that determines the activity of the operon as a whole.
when lactose is absent
a repressor protein binds a region known as the operator, blocking transcription of the structural genes.
when lactose is present
it is converted to allolactose, which binds to the repressor at an allosteric site. This prevents the protein from binding to the operator. This allows RNA plymerase to transcribe the structural genes.
presence of an inducer
inactivates the repressor, permitting the gene or operon to be transcribed.
enzyme induction
inducible gene isn't transcribed unless a specific inducer inactivates its repressor. code for enzymes in catabolic pthway.
repressible operons
usually turned on. anabolc pthways
Intracellular tryptophan levels low.
Repressor protein is inactive to prevent transcription b/c it can't bind to the operator
Intracellular tryptophan levels increase.
the a.a. trytophan (corepressor) binds to an allosteric site on the repressor. The resulting form of the repressor binds to the operator region, blocking transcription of the operon until trytophan is again required.
TATA box
promoter region in eukaryotes.
UPEs
upstream promoter elements. more present..more strongly gene is expressed
enhancers
dna sequences that increase transcription rate
transcription factors
stimulate transcription. must be present for enhancers and UPEs to be active.
heterochromatin
tightly condensed chromatin. genes in this region are turned off.
euchromatin
decondensed. actively transcribing mRNA, switched on.
transcription factors
stimulate transcription. must be present for enhancers and UPEs to be active.
heterochromatin
tightly condensed chromatin. genes in this region are turned off.
euchromatin
decondensed. actively transcribing mRNA, switched on.