Regulation of Gene Expression Flashcards
what activates or repress genes?
DNA BINDING PROTEINS
undergo non-covalent binding at the promoter
recruits RNA polymerase or inhibits it
what is the operator?
part of the operon that determines whether transcription will take place
overlaps with 3’ end of promoter and 5’ end of transcription start site
what are the types of regulatory proteins?
negative –> inhibit transcription (blocks binding of RNA polymerase)
positive –> stimulate transcription
what are the two types of operons?
inducible –> normally off, gets turned on
repressible normally on, get turned off
what is a negative inducible operon?
regulator protein is an inhibitor
a cofactor can bind to the repressor, causing a conformational change that stops it from binding
allows RNA polymerase to activate transcription
what is a negative repressible operon?
regulator protein is a repressor, but needs a cofactor to bind to the promotor
repressor is inactive without cofactor
what is positive control?
regulator protein is an ACTIVATOR
induces transcription
e. Catabolite Activator Protein
describe the elements in the lac operon
regulator protein –> inhibitor
allolactase –> inducer
CAP + cAMP –> enhancers
what enzymes are involves with lac?
Permease (lacY) –> transportation across membranes
B-galactosidase (lacZ) –> breaks down lactose into glucose
Thioglactoside Transacetylase (lacA)
common promotor (lacP)
what is coordinate induction?
simultaneous synthesis of several proteins by an inducer
describe the lac mechanism
lactose is converted into galactose and allolactase when repressor is “on”
allolactase binds to the repressor to release it from the operon
RNA polymerase binds to the promoter and induces the expression of lacZ, lacY, lacA
once allolactose is depleted, repressor can rebind to operon
what is CIS regulation?
control of gene expression on same piece of DNA
what is trans regulation?
control of gene expression on a different piece of DNA
