Flashcards in Prokaryotic gene regulation Deck (17):
what is the job of an activator gene?
- bind with complementary area of a promotor to activate RNA polymerase to transcribe the mRNA
what happens if the activator gene is degraded?
transcriptional induction of the operon is prevented
what is the job of the repressor gene?
inhibit transcription of an operon
what is an inducible operon?
usually off but can be stimulated
what does the lac operon code for?
functional genes which code for proteins that break down lactose
what happens when lactose is present?
Lactose binds to the repressor protein changing its shape so it can no longer bind and block RNA polymerase so it begins to transcribe the operon
which way does RNA polymerase transcribe?
from the 5 prime to 3 prime end
what codes for the lac 1 repressor protein?
the lac 1 repressor gene
what is the function of protein beta galactosidase?
mediates the hydrolysis of lactose by cutting the ester bond between the 2 disaccharide
what does the reduction is lactose result in?
less lactose to bind to repressor protein so it can regain its shape and bind to the promotor sequence blocking RNA polymerase
what is a repressible operon?
usually switched on but can be inhibited
what is the name of the repressor gene for the trp operon?
what does the trp operon code for?
proteins which bind together to form tryptophan
what does tryptophan do?
alters the inactive repressor protein to active so it can now bind and the trp operon is blocked from being expressed
how does tryptophan alter the shape of the repressor protein?
by binding to an allosteric site
what is the importance of tryptophan?
it is an essential amino acid but its levels must stay constant as increased levels have negative effects