Microbiology 3-3

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Microbiology 3-3
2013-11-13 22:16:28

Study guide 3-3
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  1. 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
  2. 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
  3. Constitutive genes are:
    continually expressed genes, "housekeeping genes"
  4. Inducible 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.
  5. Repressible genes:
    • make stuff found in biosynthetic pathways. Effector molecule stops
    • expression.
    • These two types of genes have two types of control! Positive and
    • negative.
  6. Type of control: Negative control
    When Binding DNA inhibits transcription
  7. Negative control-inducible genes:
    inducers repress the protein repressors. Inducers stop the repressor from repressing.
  8. Negative control-repressible genes:
    repressor needs a corepressor to work properly and inhibit.
  9. Type of control: Positive control
    DNA binding promotes transcription initiation
  10. Positive control- inducible genes:
    Activator protein needs inducer to work. Activator proteins need inducers to transcribe.
  11. Positive control- repressible genes:
    activator protein needs inhibitor to not work
  12. Explain what an operon is:
    the sequence of bases coding forĀ  one or more polypeptides together with promoter and operator/activator binding sites.
  13. 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)
  14. Characterize the following parts of an operon: Multiple Genes
    • Lac Z(beta-galactosidase),
    • LacY(encodes lactose permease), LacA (makes galactosidase transacetylase)
  15. Characterize the following parts of an operon: Control sequences-Promoter
    signals the beginning of transcription. RNA poly binds here
  16. Characterize the following parts of an operon: Control sequences- Operator
    Where the repressor binds.
  17. 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.