Chapter 18 Flashcards
gene expression in three levels
1) transcriptional control
2) translational control
3) post-translational control
what is transcriptional control?
regulatory proteins affect the ability of RNA polymerase to ind to the promoter and initiate transcription
what is translational control?
regulatory proteins alter interact with mRNA and affect it’s stability, or interact with ribosomes to affect translation initiation or elongation
what is post- transcriptional control?
chemical modifications to a protein (phosphorylation) affect its activity
which form of regulation is least wasteful?
transcriptional control
which form of regulation is most wasteful?
post-translational control
what is negative control?
regulatory protein shuts down transcription
what is positive control?
regulatory protein triggers transcription
Do bacteria need to use all of their genes all of the time experiment details.
will E.coli produce beta-galactosidase on glucose and lactose plates?
- does not produce is glucose is present
- done by Jacques Monod
Jacob and Monod genetic screen details of experiment
- mutagenesis on a large number of individuals
- genetic screen: find individuals with defects
steps: - grow mutant E.coli on a master plate
- transfer cells onto block
- transfer cells from block to replica plate with lactose
- observe if any cells fail to grow into colonies
what does galactoside permease do?
transports lactose into the cell
what does beta-galactosidase do?
breaks down lactose inside the cell
what does the mutation in lacZ do?
- mutant lack functional b-galactosidase
- brings in lactose but can’t break it down, results in excess lactose
what does the mutation in lacY do?
- mutants lack galacoside permease so they can not transport lactose into the cell
what does the mutation in lacI do?
- produce b-galactoside and galactoside permease when lactose is absent
