Chapter 16 - Control of Gene Expression in Prokaryotes Flashcards
A(n) __________ operon is normally turned on, and it is turned off by a(n) _________.
repressible; repressor
For a(n) __________ operon, transcription normally does NOT take place, and it is kept off by a(n) _________.
Inducible; repressor
The lac operon is an example of a __ __ genetic system because the binding of the lac __ to the operator inhibits transcription by RNA polymerase.
negative inducible; repressor
Low levels of glucose lead to all of the following except: A. cAMP levels increase B. permease levels increase C. β-galactosidase levels increase D. the lac operon is activated E. CAP-cAMP loses its affinity for DNA
E. CAP-cAMP loses its affinity for DNA
A critical part of gene regulation requires __ proteins which have binding __. Commonly found within __ are __: simple proteins structures that include__-loop-__, __ fingers, and __ zipper.
regulatory; domains
domains; motifs; helix-loop-helix; zinc; leucine
Regulatory protein motifs: describe a helix-turn-helix.
Two 𝜶-helices connected by a turn. The helices fit into the grooves of DNA.
Regulatory protein motifs: describe zinc fingers
Finger-shaped loops of AAs associated with a zinc ion. The fingers fit into the major groove of DNA.
Regulatory protein motifs: describe leucine zippers.
Helix of leucine residues and an arm of basic AAs that bind to two adjacent major grooves.
How do amino acids in DNA-binding proteins interact with DNA?
a. By forming covalent bonds with DNA bases
b. By forming hydrogen bonds with DNA bases
c. By forming covalent bonds with DNA sugars
b. By forming hydrogen bonds with DNA bases
In bacteria, genes with related functions, called __, are clustered together and often transcribed into a ___ mRNA. They are regulated by a __ gene that is not part of the ___.
operons, single
regulatory; operon
Operons are regulated by ___ ___. They function by binding to the ___ (part of the operon) and either __ or __ transcription.
regulatory proteins.
operator; induce; repress
In negative inducible operons, the regulatory protein is a __ and __ transcription. The regulatory protein is made in __ form.
Because the operon is inducible, transcription requires an ___ to bind to and __ the regulatory protein (the __ causes an __ change in the regulatory protein). Note: precursor to the final product is usually the ____.
repressor; blocks
active
inducer; inactivate; inducer; allosteric
inducer
In negative repressible operons, the regulatory protein is a __ and __ transcription. The regulatory protein is normally ___ until a ___ binds to it; once this occurs, the regulatory protein binds to and __ transcription (binding of the ___ causes ___ changes that activate the regulatory protein). Note: the product usually serves as the ___.
repressor; stops.
inactive; corepressor
stops/represses; corepressor; allosteric
corepressor
In positive inducible operons, the regulatory protein is made in __ form; it requires an __ to bind to it, which will cause an __ change and promote binding to the __, which will __ transcription. Note: the product precursor usually serves as the ___.
inactive; inducer; allosteric; operator; start/induce
inducer
In positive repressible operons, the regulatory protein is usually in ___ form and __ transcription. When a ___ binds to the regulatory protein, ___ changes cause ___ of the protein from the operator, and transcription __. Note: the product usually serves as the ___.
active; promotes
corepressor; allosteric; dissociation; stops/repressed.
corepressor
In the 60’s, Jacob and Monad were able to identify and describe the operon model by using what?
classical genetics using mutations to determine how transcription was regulated.
E. coli must transport lactose across the membrane to metabolize it. This requires __ (lacY gene product). The disaccharide must be broken down by _-__ (lacZ product). A third gene, LacA, codes for __ __, but nobody knows WTF it does. All 3 genes are structural and are transcribed as a __ mRNA - that makes the mRNA __. The __ protein is made by (lacI). The __ is an element called lacO.
permease
β-galactosidase
thiogalctoside transacetylase
single; polycystronic
regulatory
operator
β-galactosidase performs 2 functions; it breaks the bond of __ to yeild __ and __; and it changes the bond to yield ___ (a stereoisomer of lactose).
lactose; galactose; glucose
allolactose
In the absence of lactose, the regulatory protein, a __, binds to the operator and __ transcription. Only the presence of lactose can __ transcription. This form of regulation is __ __.
repressor; inhibits/represses.
induce
negative inducible.
In the lac operon, the presence of lactose causes __ changes to the regulatory protein (a __) which, in turn, causes ___ of the protein, so transcription is ___. This form of regulation is __ __.
allosteric; repressor; dissociation; induced.
negative inducible.
The operator of the lac operon overlaps the __ and the _’ of the __ gene.
promoter; 5’; lacZ
___ of the lac operon is __ 100%. The cells __ have low __ of the 3 protein products. When lactose is available, __ transports a small amount, _-__ coverts some of it to __ which acts as the __.
repression; never
always; levels
permease; β-galactosidase; allolactose; inducer
Lab work with the lac operon usually uses __ instead of lactose; __ can’t be __.
IPTG; IPTG; metabolized
Two levels of regulation for the lac operon are:
(1) __ __: binding of the lac repressor to the operator ___ transcription. (2) __ __ binding of __ __ __ (CAP) stimulates transcription (contingent on glucose levels being __).
negative inducible; blocks
positive inducible; catabolite activator protein; low
