Chapter 12-test 2 Flashcards
(17 cards)
constitutive transcription
bacterial genes function continuously
regulated transcription
Others are needed only in response to envir changes. control of both initiation and amount of transcription
Positive control of transcription
binding of an activator protein to regulatory DNA and initiating gene transcription
Negative control of transcription
binding of a repressor protein to a regulatory DNA sequence and preventing transcription
Repressor proteins
genes/operons are normally on and turned off by signal. bind to operators which block transc. initiation.
repressor proteins
DNA binding domain
has amino acids w side chains. has H, N, and O
repressor proteins
allosteric domain
binds molecule/protein, causes change in protein that activates dna binding domain.
inducers
Some repressors can be inactivated by inducers.
corepressors
Other repressors can be activated by corepressors
effectors
Some activators can be activated
inhibitors
Other activators can be inhibited by inhibitors
lactose (lac) operon of E. coli
produces 3 polypeptides needed for using lactose as fuel
tryptophan (trp) operon of E. coli
produces enzymes needed for the biosynthesis of the amino acid Trp
what do bacteria need to live their lives?
energy
preferred energy source of e coli
glucose. lactose: alternate energy source.
Bacteria will use lactose when there
is plenty lactose around but first
they have to bring it into the cell, then break it into Glu + Gal.
lac Operon Structural Genes
- lacZ, which encodes b-galactosidase
- lacY, which encodes the enzyme permease
- lacA, which encodes transacetylase (“unclear” function)
