7.4 Gene Expression Flashcards
are all proteins required for gene expression?
no, and intricate systems ensure all cells express genes required; gene expression responds to cellular environment
insulin
hormone produced by pancreas that lowered blood glucose levels by promoting more glucose
housekeeping cells
some proteins needed all the time to regulate processes like metabolism, growth, and DNA replication and transcription
lac operon
cluster of genes that contain DNA sequences to regulate metabolism of lactose
- consists of promoter, operator, coding regions for enzyme to metabolize lactose
operator
region in operon that has regulatory factors bind to repressor protein
repressor protein
binds to operator to repress gene transcription
no lactose?
lac repressor is active and binds to operator
lactose present?
some binds to repressor and is rendered inactive and cannot bind to operator blocking transcription
as concentration of lactose decreases?
amount of inactivated repressor decreases
inducer
signal molecule that triggers gene expression of operon
trp operon
regulates production of tryptophan in a cell
tryptophan
important amino acid used to build proteins
when is trp activated and inactivated?
activated in presence of tryptophan, inactivated in absence
when tryptophan is present?
cell can conserve energy by using available and and stopping transcription of gene that code for enzymes involved in biosynthesis of amino acid
when tryptophan is absent?
repressor protein is inactive and doesn’t bind to operate; RNA polymerase binds to promoter and transcription of genes for biosynthesis can proceed