Term
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Definition
| Where the genes are arranged that they are all transcribed on a single message |
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Term
| How is the operon regulated? |
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Definition
Cis-Sequences of DNA associated with operon
Trans- regulated by DNA not associateed with operon |
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Term
| What happens if tryptophan is absent, and the operon is active? |
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Definition
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Term
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Definition
| RNA Polymerase binding site-site of transcription intitiation |
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Term
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Definition
Blocks polymerase from moving forward once it binds
Sequence near the promoter that binds repressor protein, blocking RNA |
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Term
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Definition
| Protein that bind operator |
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Term
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Definition
| Small molecules that binds repressor and allows it to tblock transcription |
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Term
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Definition
| A small molecule that binds |
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Term
| When does E coli use lactose as energy source? |
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Definition
When Lactose is present
When Glucose is absent (or else it can use glucose directly) |
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Term
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Definition
disaccharide. glucose + glucose
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Term
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Definition
| Faulty by product of reaction of lactose break down-used as an indicator of the presence of lactose |
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Term
| WHat does the Lac operon consist of? |
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Definition
3 genes for lactose metabolism
LacZ- B-galactosidase
LacY- lactose permease
LacA= transacetylase |
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Term
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Definition
| cleaves lactose (or rearranges it int allolactose) |
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Term
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Definition
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Term
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Definition
| Acetylates(functional group that modifies behavior of protein) B-galactosidase, modifying its activity |
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Term
| What is the order in which three genes are on a polysistic message? |
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Definition
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Term
| Describe negative regulation int the Lac Operon |
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Definition
when the promoter is turned off when substrate is absent
Lac I-(extra gene involved) the Lac repressor blocks transcription when there is no lactose
Cell wont waste energy making enzymes when no substrate is present |
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Term
| Describe the Positive regulation in the Lac Operon |
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Definition
Promoter is turned up when energy (glucose) is needed
CAP- catabolite activator protein increases promoter function when glucose is low
Cell won't waste energy making glucose from lactose when it has plenty of glucose |
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Term
| What does the Lac repressor do? |
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Definition
When lactose is absent, turns promoter off
Lac repressor binds |
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Term
| When lacotose is present, what occurs to the promoter? |
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Definition
When lactose is present, promoter is ‘on’
Small amount of β-galactosidase made via ‘leaky’ repression
converts some of the lactose into allolactose
Allolactose serves as an indicator of lactose presence
Allolactose is an inducer, inactivating Lac repressor
Allosteric regulation – it changes its shape so it can’t bind promoter
Promoter is available for RNA polymerase to bind and
transcribe operon |
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Term
Where does gene regulation occur in eukaryotics? |
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Definition
| can occur at every step in process of expression |
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Term
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Definition
DNA in association with proteins
DNA is highly folded and tightly packed
Packed DNA is unavailable for transcription |
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Term
| When glucose is absent, what happens? |
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Definition
◦ CAP – catabolite activator protein
When glucose is absent, promoter is ‘high’
cAMP is a cellular indicator for low glucose
cAMP binds to CAP
CAP binds to Activator sequence adjacent to promoter
RNA polymerase binds CAP and is efficiently loaded onto promoter
Remember, though, that operon is only transcribed when lactose is
present, due to lac repressor |
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Term
| What are the 4 possible conditions of the Lac operon? |
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Definition
G=Glucose L=Lactose
G present L absent = not much RNA made
G present L present = not much RNA made
G absent L absent = not much RNA made
G absent L present = Very much RNA made |
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Term
| How do eukaryotics do gene regulation? |
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Definition
Energy conservation
◦ Response to environment
◦ Cell specialization
Development
Function
◦ Growth regulation (cancer) |
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Term
| Where does gene regulation occur in eukaryotes? |
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Definition
Every step in process
Transcription
Indirect – regulation of chromatin
structure
Direct – Promoter regulation
Post-transcriptional
mRNA processing
mRNA transport
mRNA stability
Translation
Protein processing
Protein transport
Protein stability |
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Term
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Definition
◦ DNA wraps around histone proteins
◦ Histone proteins associate into larger
clusters
Heterochromatin
Highly condensed, not available for expression
◦ Acetylation of tails prevents association
Euchromatin
DNA is less condensed, available
for expression
◦ Transcription can be
regulated by histone
acetylation near gene |
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Term
| What tends to be clustered in different subdomains within the nucleus |
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Definition
| Heterochromatin and euchromatin |
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Term
| What controls elements (DNA) bind to transcription factors(proteins) |
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Definition
enhancers- binding sites for activating proteins (Activators)
Repressors- binding sites for repressing proteins |
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Term
| Describe eukaryotic transcriptional regulation |
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Definition
Transcription factors help load (or block loading) or polymerase
Action at a distance communicate via DNA bending
work through intermediary protein complex
Extracellular signals can regulate transcription |
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Term
| Describe the intermediary protein complex in eukaryotic transcriptional regulation |
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Definition
| Mediator loads polymerase and can also recruit enzymes that carry out chromatin modification |
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Term
| What can lead to loss of appropriate transcriptional control |
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Definition
| mutations in pathway proteins-cancer |
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Term
| Describe post-transcriptional Regulation |
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Definition
Alternative splicing- can also get alternative polyadelylation
mRNA stability
Translational regulation |
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Term
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Definition
| making small complementary RNAs can result in mRNA being destroyed |
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Term
| What is Translational regulation? |
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Definition
| protein binding or formation of localized dsRNA can inhibit accessibility to ribosome |
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