Term
| What does the lac operon look like? What binds where? Include the regulatory genes that come before? |
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Definition
POZYA;
-P; *promotor - bind RNA pol and CAP (CRP)
-O; *operator - binds repressor
-Z; B-galactosidase
-Y; Permease
-A; Transacetylase
-Before it we have Pi & I for Promotor and Inhibitor (*repressor is the correct term)
-Remember, *lac binds the repressor (acts as *inducer); reason the lac operon is an *inducible operon |
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Term
| How does glucose play a role in lactose production? |
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Definition
-It inhibits the production of *cAMP which is needed to complex with *CAP (aka CRP), which then binds to the *promotor allowing RNA pol to bind
-This is called catabolite repression |
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Term
| What is the difference between Cis-active and Trans-active regulatory sequences? |
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Definition
| -Cis are in the operon (promotor, and operator) and trans is outside of the operon (repressor gene) |
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Term
| -If we note a cell as being I-O+Z+/I+O+Z-, what does that mean and what will be the production of beta-gal? |
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Definition
-Means that the lac region is diploid
-On the first one we have no repressor (I), so alone it would be constitutive
-On the second one we have to Z (no B-galactosidase), so alone we would not get product
-Adding them together however, the cell will have **inducible production of B-gal |
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Term
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Definition
-A group of operons under control of a single regulatory protein
-This would be typical of virulence genes (all get activated when the stimulus is received) |
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Term
| What is tryptophan considered in the Trp operon? |
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Definition
-It acts as a corepressor, binding to the repressor, which then binds to the operator sequence
-This is the reason Trp is a *repressible operon; a common theme in transcription with an anabolic end goal (lac has catabolic end goal) |
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Term
| What does the Trp operon look like? |
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Definition
-POLED CBA
-L is the *leader sequence containing the **attenuator
-trpE-A (backwards) are structural genes
-Before this, we have another *TrpR (for repressor) which has it's own operator and produces whats called an **aporepressor (requires co-repressor) |
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Term
| What mutations in the Trp operon will cause constitutive expression? |
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Definition
| -Mutation in the operator sequence, or in genes coding for the repressor that binds it will give constitutive expression |
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Term
| Explain how the leader sequence works? |
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Definition
-It has a couple of codons that code for tryptophan, and since transcription and translation occur at the same time, the RNA Pol will "know" if trp is around or not
-Basically, unless the ribosome *stalls at the trp codons, an unfavorable *stem-loop will form at the **attenuator sequence and transcription will be terminated
-A different, favorable loop will form if the ribosome is stalled (2-3 loop good, 3-4 loop bad) |
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Term
| What is the stringent response? What is the gene for it? What happens when it is mutated? |
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Definition
-It is the down-regulation of *stable RNA (tRNA & rRNA) in response to AA depletion/starvation
-**RelA is the gene, and when it is mutated we get a *relaxed cell that synthesizes stable RNA even during AA starvation |
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Term
| What does RelA code for? When does it code for product? |
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Definition
-Codes for *ribosome-associated stringent factor which synthesizes **guanosine tetraphosphate (ppGpp)
-ppGpp is the signal for the stringent response
-RelA is engaged when a ribosome is occupied by an *uncharged tRNA
-It works because the stable RNA is pretty much always being associated with proteins; so why bother if out of AA |
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Term
| How does a bacteria regulate production of it's virulence factors? What are the proteins involved in Bordetella pertussis? |
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Definition
-Works in a *two-component regulatory system with sensor & regulator proteins
-An external signal is received by a membrane **kinase which then phosphorylates a **response regulator (does repression or activation)
-BvgS/BvgA (sensor/regulator for B. pertussis) |
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Term
| What is antigenic variation? How does it work? Give an example of a disease? |
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Definition
-A change in the surface molecules
-It is caused by genetic rearrangements that occur at a high frequency within a population
-An example would be pili in N. gonorrhoeae |
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Term
| What is phase variation? What are the two ways it can occur? |
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Definition
-It is when gene products are turned on or off
-The first method involves the inversion of a DNA segment which contains a promoter
-The second method is the variation in the occurrence of short segments at the 5' end (not divisible by three, so they disrupt the reading frame unless in appropriate #) |
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