Pharm 411: Regulation of Gene Expression Flashcards Preview

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1

What are the stages that regulation of gene expression can occur?

Before making the RNA -Transcriptional regulation
Before making the protein - translational regulation
After making the protein - post translational regulation (could be like phosphylation to activate or not)

2

Do all genes get regulated?

No, some genes are always on and its called constituively active
Something like a ribosome would fall into this because we use it so often we always need to make them

3

What is the most common type of regulation and why?

Its transcriptional regulation
This is because its the most energy economical meaning that regulate it before you make it you dont waste the energy in building it and then not using it

4

What are the two ways in which transcriptional regulation can occur in prokaryotes?

Cis-acting elements
trans-acting factors

5

What are cis-acting elements for prokaryotes in transcriptional regulation

Sections of DNA near the gene which control transcription
Normally found in noncoding regions of the genome
Known as promoters, operators, silencers, enhancers and hormone response elements

6

What are trans-acting factors for prokaryotes in transcriptional regulation

Proteins or other molecules which bind to the DNA
They interact with the DNA and activate or repress transcription
They usually bind to cis-acting elements

7

What is the prokaryotic operon

A cluster of genes only in porkaryotes with related functions acting as a coordinated unit controlled by a common regulatory sequence
*they all respond to the same control mechs

8

What is an operon composed of?

1. structural genes which code for the proteins for desired function
2. Promoter region which influences the efficiency of transcription
3. An operator which is a sequence of DNA which can bind a repressor and/or an activator
4. Repressor gene which codes for a protein which inhibits transcription when bound to DNA
5. Activator gene which codes for a protein which enhances transcription when bound to DNA

9

What is the prokaryotic promoter?

A sequence of DNA that influences how frequently a gene is transcribed
Usually found upstream (towards 5' end) from the gene

10

What is meant by the promoter regions have consensus sequence of DNA?

A consensus sequence is the sequence of bases that are most commonly found
*If a promotor is more similar to the consensus sequence, the better the promoter and the more often the gene will be transcribed

11

What is the prokaryotic operators?

Sequence of DNA to which regulatory proteins (repressors and activators) bind

12

What is different about the operators compared to the promotors in terms of where they bind?

They dont need a consensus sequence
They dont have a common location and can bind upstream or down stream to the promoter

13

What kind of control do prokaryotic operators exert?

Negative control
Positive control

14

What is negative control of the prokaryotic operator?

A repressor protein binds directly to the operator blocking RNA polymerase turning OFF the gene

15

What is positive control of the prokaryotic operator?

activator protein binds directly to the operator stimulating RNA polymerase BINDING which turn ON the gene expression

16

What are effectors?

They are small molecules or signaling peptides that exert control on transcription thro operators

17

What are the two types of control that an effector can have?

Inducible control
Repressive control

18

What is inducible control caused by an effector

Binding of and effector turns ON transcription

19

What is repressible control caused by an effector?

Binding of effector shuts OFF transcription

20

What is Negative Inducible control?

A repressor protein binds to the operator and block transcription WITHOUT effector. An inducer can then bind to the repressor causing it to leave the operator and turn on transcription

21

What is negative repressible control?

Repressor protein WONT BIND the operator without an effector. A corepressor BINDs to the repressor and causes it to bind to the operator turning OFF transcription

22

What is positive inducible control?

Activator protein wont bind to operator without an effector. An inducer binds to the activator and causes it to bind to the operator turning on transcription

23

What is positive repressible control?

Activator protein binds to the operator and activates transcription without effector. An inhibitor bind to the activator causing it to leave the operator turning off transcription

24

What is a Catabolic operon?

Codes for enzymes used in pathways to break down substances
*kept off until the substance is present
*Usually under inducible control

25

What is an Anabolic operon?

Code for enzymes used in pathways to synthesize substances
*Kept on until there is too much substance
*usually under repressible control

26

What is the lac operon?

Its a catabolic operon that codes for three proteins that are necessary for the breakdown and utilization of lactose
*lac (lactose)

27

What are the two mechanisms which control the lac operon?

1. A repressor which binds to an operator region
2. Inducers which bind to an operator ( CAP-binding site)

28

What is the status of the repressor protein on the mRNA for the lac operon?

It is always transcribed (uncontrolled) this means the repressor is always available
*the repressor bound to the operator block RNA polymerase
*The genes needed to breakdown lactose are not normally produced

29

What does control of the lac operon depend upon?

Both the levels of glucose and lactose

30

What is the signal for glucose levels?

cAMP, When glucose levels are high it blocks the production of cAMP
When glucose levels fall you activate glyogen to bind the the Adenylate cylclase system which will produce cAMP
**TLDR: High glucose = no cAMP, low glucose = cAMP