Exam 2: Ch 7 Control of Gene Expression in Bacteria Flashcards
in cancer, genes that restrain cell growth are ________ repressed and genes that encode proteins that promote cell growth and replication are ________ activated
abnormally, inapropriately
regulation of gene expression can occur at various steps
transcription initiation and elongation
RNA processing
mRNA export from nucleus
translation
control of gene expression at which two steps are most important for determining whether most genes are expressed and how much protein is produced?
transcription initiation and elongation
what is pax6
transcription factor that regulates transcription of genes involved in eye development
what do repressor and activator proteins do
recognize and bind to specific regions of DNA to control the transcription of a nearby gene
transcription control region
sequences of DNA that serve as binding sites for repressor and activator proteins
the structure and function of a cell are determined by …
the proteins it contains
by controlling _____ a cell can regulate which proteins it produces, and how rapidly
transcription
when transcription of a gene is ______, the corresponding mRNA and encoded protein is synthesized at low rates. Opposite of this is…
repressed
activated
operons in E. coli
make up half the genes
encode enzymes involved in metabolic pathways or multiple proteins
what do the lac and trp operon encode?
lac: 3 proteins required for metabolism of lactose
trp: 5 pp needed for biosynthesis of tryptophan
coordinate regulation
all genes in an operon are activated or repressed to the same extent
transcription of operons and isolated genes is controlled by interplay between…
RNA polymerase and specific repressor and activator proteins
to initiate transcription, E. coli RNA polymerase must be associated with…
a sigma factor
σ70 binds RNA polymerase and to promoter DNA sequences
σ70 is…
an initiation factor
synthesis of the lac operon is repressed when….
there is no lactose around: to conserve energy
when there is glucose around: preferential glucose metabolism
transcription of lac operon under different conditions is controlled by…
lac repressor
catabolite activator protein (CAP)
both bind to a specific DNA sequence in the lac transcription control region called the operator and CAP site
when no lactose is present where does the lac repressor bind
to the lac promoter, blocking σ70 from initiating transcription
when glucose falls, E. coli synthesizes a lot of…
cyclic AMP that binds to CAP protein allowing it to bind to the CAP site, stimulating rate of transcription initiation
what makes a strong/weak promoter
rate of transcription
what regulates expression of many bacterial genes via DNA-binding repressors and activators
small molecules
cAMP, phosphorylation
how many σ factors are there
7
enhancer
binding sites in DNA located 80-160bp upstream from start site
σ54
sigma factor found in E. coli
binds to RNA polymerase to start transcription initiation
NtrC protein
stimulates transcription of glnA gene that encodes enzyme glutamine synthetase
binds to enhancer after being phosphorylated by NrtB
many bacterial responses are controlled by..
two-component regulatory systems
like NtrC and NtrB
control of transcription elongation example
trp operon
trp operon is repressed by
trp repressor when concentration of trp in cytoplasm is high
when there is low concentration of tRNAtrp…
the ribosome stalls at the 2 Trp codons in region 1
riboswitch
RNA tertiary structures that bind small molecules when present at high concentration
form hairpins that lead to early termination of transcription
