Gene Expression III - Gene Regulation (c14) Flashcards
(21 cards)
gene regulation
the ability of the cell to control levels of gene expression
metabolic control
control protein levels for enzymes that catalyze biochemical reactions
response to environment
respond to environmental stimuli
response to stress
respond to stressors in the cell
conservation of energy
make only proteins that are necessary at any given time
gene regulation in prokaryotes
prokaryotes are constantly regulating expression of metabolic genes in response to molecules in their environment
when lactose is available, bacteria synthesizes what two proteins
lactose permease
B-galactosidase
lactose permease
transports lactose into cell
B-galactosidase
breaks down lactose
gene regulation in eukaryotes
multicellular eukaryotes develop many different cell types with unique functions – cell differentiation
each eukaryotic cell type differentially regulates gene expression
all organisms cells contain same genome but express different proteomes
expression is differentially regulated during development
difference between eukaryotic and prokaryotic gene regulation
prokaryotes uses lactose, all same cell
eukaryotes contain same genome but express different proteomes
only eukaryotes regulate gene expression at the post-transcriptional level
housekeeping genes
genes that are ubiquitously expressed regardless of cell type
most gene regulation occurs at . . .
transcriptional and post-translational levels in BOTH eukaryotes and prokaryotes
transcriptional regulation in bacteria
involves transcription factors , repressors inhibit transcription of genes when not needed, activators activate transcription of genes when needed
operon
a cluster of genes in bacteria that are under transcriptional control of one promoter
operons in bacteria
allow coordinated regulation of a group of genes that share a common function
lac operon
encodes a cluster of genes involved in lactose catabolism (lacZ, lacY, lacA)
two transcriptional regulatory sites
cap site: bound by activator
operator (lacO): bound by repressor
lacyY codes for lactose permease: transports lactose into the cytosol
lacZ codes for B-galactosidase: breaks down lactose into galactose and glucose
lac operon with no lactose
lac repressor binds the lacO operator and inhibits transcription
lac operon with lactose
small amount of allolactose is made
Rna polymerase is now free to start transcription of the lac genes
allolactose
a small molecule that binds and inhibits the lac repressor
