Kandpal- Promoter, polymerases and transcription factors Flashcards
what is the purpose of house keeping genes (constitutive)?
required for general cell functions and cell viability. usually used in basic metabolism and proteins for cell structures (ribosomes)
what are the functions of regulated genes (inducible)?
cell-type specific genes which are responsible for the differentiated functions of specific cell typess. examples: hormone/growth, factor/stress responsive genes.
in eukaryotes what does gene regulation control?
growth, development, differentiation, cell to cell communication
why is gene regulation important in prokaryotes?
adjustment of metabolic requirement in response to nutritional environment
how is the synthetic pathway activated?
absense of the end product leads to activation of synthetic pathway
when will trp synthesis begin?
in the absence of tryptophan
what three things make up an operon?
protein coding genes, shared promoter and regulatory site
what is the role of lactose permease?
designated as Y (transport)
what is the role of beta-galactosidase-Z?
cleaves lactose into galactose and glucose
what is the role of galactoside transacetylase-A?
nonmetabolites removal
in what genes can the enzymes permease, galactosidase and transacetylase be found?
found in the polycistronic
when will the Lac repressor (tetrameric protein) occupy the operator of the Lac Operon?
in the absence of lactose.
what else is inhibited when the lac repressor is bound to the Lac Operon?
binding of RNA polymerase to the promoter is excluded. Lactose metabolizing genes are not transcribed
when will the affinity for the repressor be reduced for the operator?
in the presence of lactose (Lactose will bind to the repressor, which alters the repressors affinity for the operator)
when E. coli was grown in a mixture of glucose and lactose, which substrate did the bacteria favor?
glucose
what effect does glucose have on lactose?
glucose represses lactose metabolizing enzymes and many other catabolic enzymes. this is known as “Catabolite Repression”
what are the levels of cAMP in the presence of glucose?
they are low
what is the function of cAMP?
needed for activation of DNA binding protein CAP and for transcription of ‘lac’ operon
what are the required criteria for the Lac Operon?
the Lac operon will be active if only lactose is present and glucose is absent (remember how glucose lowers cAMP levels)
what transcribes class 1 genes?
transcribed by RNA Polymerase 1.
rRNA (28S,18S, 5.8S)
what transcribes class 2 genes?
transcribed by RNA polymerase 2.
mRNA and U1 and U2 snRNA
what transcribes class 3 genes?
transcribed by RNA polymerase 3.
tRNA, 5S rRNA and snRNA
what are the three types of promoters?
TATA promoters, Initiator (Inr) promoters and TATA-less and initiator-less promoters
where is TATA sequence located?
at 25 to 35
