Card Set Information
Study guide 3-3
Identify the levels at which gene expression is regulated in bacteria:
Transcription:Regulatory proteins decide when transcription starts, Attenuation, and Riboswitches
Translation:Prevent Translation, Antisense RNA, Riboswitch
: Protein Inhibition, covalent modification
Identify the levels at which gene expression is regulated in Archaea:
Transcription:Regulatory proteins bind to DNA, control transcription starting. Compaction of Chromatin
Translation:Antisense RNA binds to mRNA
: feedback inhibition and
Constitutive genes are:
continually expressed genes, "housekeeping genes"
when an inducer is present it increases its production, it is expressed in response to an effector molecule. Normally not expressed but when a specific molecule is present it
make stuff found in biosynthetic pathways. Effector molecule stops
These two types of genes have two types of control! Positive and
Type of control: Negative control
When Binding DNA inhibits transcription
Negative control-inducible genes:
inducers repress the protein repressors. Inducers stop the repressor from repressing.
Negative control-repressible genes:
repressor needs a corepressor to work properly and inhibit.
Type of control: Positive control
DNA binding promotes transcription initiation
Positive control- inducible genes:
Activator protein needs inducer to work. Activator proteins need inducers to transcribe.
Positive control- repressible genes:
activator protein needs inhibitor to not work
Explain what an operon is:
the sequence of bases coding for one or more polypeptides together with promoter and operator/activator binding sites.
Characterize the parts of the operon: LacI, CAP, Operator
The lac operon codes for 3 proteins required for the catabolism of
lactose. Z,Y, and A. The LACI codes for the repressor (lac repressor), the CAP
site is like the activator binding site. Operator (repressor binds here)
Characterize the following parts of an operon: Multiple Genes
LacY(encodes lactose permease), LacA (makes galactosidase transacetylase)
Characterize the following parts of an operon: Control sequences-Promoter
signals the beginning of transcription. RNA poly binds here
Characterize the following parts of an operon: Control sequences- Operator
Where the repressor binds.
Describe negative transcriptional control of the lac operon
Lac repressor is a tetramer. The tetramer is formed when two dimers interact.
When lactose catabolism isn't needed each dimer tightly binds to one of 3 different lac operator sites. (O1, O2, O3)
O1-main operator, must be bound to stop.
When both bind to O1 and Ox the dimers bring the sites close together.
A loop of DNA forms between them.