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
corepressor
signal molecule that binds to regulatory protein to reduce expression of operon’s genes
eukaryotic control mechanisms
transcriptional
post-transcriptional
translational
post-translational
transcriptional
regulates which genes are being transcribes (DNA to RNA) or controls rate at which transcription occurs; activator and repressor proteins bind to promoter and enhance or decrease rate of transcription, methyl groups added to cytosine bases in promoter –> RNA polymerase cannot bind and transcribe
post-transcriptional
controls availability of mRNA molecules to ribosomes; pre-mRNA molecules undergo changes in nucleus, resulting in final mRNA before translation; alternative splicing occurs; diff combos of introns are removed and exons are spliced together
translational
controls how often and how rapidly mRNA transcripts will be translated into proteins; variation of length of poly(A) tail related to rate of translation
post-translational
controls when proteins become fully functional, how long they are functional, and when they’re degraded; presence of hormones may lengthen or shorten length of time that a protein is functional
