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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
- Posttranslation: 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
- Posttranslation: 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
- will be.
- 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
- Lac Z(beta-galactosidase),
- 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.