gene regulation Flashcards
tryptophan operator: normally on or off?
normally on
operon
a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter.
tryp operon: negative or positive regulation?
negative regulation. controlled by a repressor protein - (aka normally, RNA polymerase is able to smoothly ride the RNA, but when something activates the repressor protein aka presence of tryptophan, it sits down and prevents RNA polymerase from sitting down
where would a repressor protein bind when it activates
the operator sequence on the DNA
activator protein
when an activator protein is present and active, it binds to an activator site on the RNA and turns genes ON
if you have an activator protein is this positive or negative regulation
positive
lac operon- normally on or off?
normally off
what two types of proteins control lac operon?
activator and repressor proteins
constitutive mutation
always on (lac operon)
CAP
catabolite activator protein- an activator protein that is itself regulated by the presence of glucose
how does glucose regulate CAP?
low glucose -> high CAP (promoter activated) and vice versa
how does lactose in the environment control the lac repressor
lactose -> allolactose -> allo binds 2 repressor, prevents it from sitting on the operator sequence like it normally does (recall lac normally off) and lets RNA sits down, begin transcribing enzymes to deal with lactose
what 2 things are necessary for lac operon to transcribe
CAP being in, and repressor not being on there
transcription factors
eukarytoes control gene expression via transcription factors, like TATA binding protein
enhancers
from a distance, tell transcription to go
how are nucleosomes involved in this whole gene regulation business?
nucleosome unwinds a little for purposes of gene expression. separate strands, some proteins jump on and signal ‘unwind’
Structural mutants
strains of bacteria that do not make functional beta-gal enzyme. Defect Is in the beta-gal enzyme (always off)
BETA GALACTOSIDASE
Enzyme that cuts lactose into glucose + galactose
what color does beta gal turn an indicator dye?
blue
of glucose, maltose and lactose- which do bacteria digest first?
bacteria prefer to digest glucose first.
francois jacob
- Name of sequence of operator: “Lac O+” (normal sequence.) mutant phenotypes: “Lac Z-“ structural mutation in beta-gal gene. “Lac Y+” . also “Lac O^c” for constitutive. “Lac Z+” “Lac Y-“
- Partial diploid because it only has extra lac operon pieces- diploid menes your entire genome is diploid!!!
Lac Y+ : working. Lac Y-: not working. Lac Z+: working. Lac Z-: not working. Normal one
