Lecture 8 Gene Regulation Flashcards Preview

BIO 425: Microbiology > Lecture 8 Gene Regulation > Flashcards

Flashcards in Lecture 8 Gene Regulation Deck (30)
Loading flashcards...
1

What is the goal of metabolic regulation?

Efficient use of resources

2

What are the types of metabolic regulation?

Gene regulation

-increase/decrease amount of protein

-slower response

 

Post-Translational Modification

-Increase/decrease activity of protein by preventing functioning of protein

-Faster response

3

What are the stages of transcription/translation that gene regulation and post-translational modification can take place?

Gene regulation

-transcription level w/ regulatory proteins

-transcription or translation level w/ RNA based regulation

 

Post-translational

-after translation....duh

4

How do we study gene expression at the protein level and at the gene level?

Protein level - reporter genes

 

Gene level - DNA sequencing

5

What are reporter genes?

Genes that code for proteins that are easy to detect/measure

-eg. green fluorescent protein

6

DNA sequencing is used to study gene expression at the gene level. How do we do it?

1. Isolate mRNA from cells

2. Transform mRNA to DNA

3. Determine identity and number DNA Sequences

7

What are regulatory proteins? What kind of structure do they have?

proteins that bind to DNA They have homodimeric structure that bind in major groove in DNA to interact w/ specific DNA sequences

8

What is the function of a regulatory protein?

Either START or STOP transcription

STOP

-block RNA polymerase=prevent transcription

START

-Bind RNA polymerase=activate transcription

9

What are the types of transcription regulation?

Negative control

-repression of mRNA synthesis

 

Positive control

-activation of mRNA synthesis

10

How does negative control of transcription work?

When regulatory protein bound to DNA

-Blocks RNA polymerase and prevents transcription

 

When regulatory protein released from DNA

-transcription possible but not automatic

11

How are enzymes used in negative control?

Enzyme Repression

-repressor+corepressor

-product abundant in cell=no additional synthesis

 

Enzyme Induction

-Repressor+Inducer

-substrate present in cell=additional synthesis

12

Go through arginine synthesis example, arg operon, for negative control repression.

Arginine acts as co-repressor

-when abundant in cell, it binds repressor and blocks transcription

-when not abundant in cell the repressor doesn't block RNA polymerase

13

Go through lactose degradation example, lac operon, for negative control induction

lactose acts as inducer

 

When lactose not abundant in cell the repressor binds DNA to block RNA polymerase

-no need for enzyme

 

When lactose abundant in cell it binds to repressor to release DNA and allow RNA polymerase to proceed

-need enzyme to break down lactose

14

What happens if ariginine is high or low in cell?  What kind of negative control is this?

 

What happens if lactose is high or low in cell?  What kind of negative control is this?

ARGININE - Repression

-High=transcription blocked

-Low=transcription proceeds

 

LACTOSE - Induction

-High=transcription proceeds

-Low=transcription blocked

15

What is positive control?

When regulatory proteins bound to DNA

-binds RNA polymerase

-activates transcription

 

When regulatory proteins released from DNA

-transcription possible but NOT automatic

16

Go through maltose catabolism, mal operon, example of activation positve control

Excess maltose in cell = time to break it down

Limited maltose in cell = no need for enzymes

 

Maltose Activator protein + Inducer

-Maltose activator protein and inducer bind allowing the complex to bind to activator binding site allowing transcription to proceed

17

What is the difference between postive and negative control?

Positive

-control DNA region = activator-binding site

-located BEFORE promoter

 

Negative

-control DNA region = Operator

-Located AFTER promoter

18

What is the activator-binding site?

Near the promoter region, where activator protein binds to allow transcription to proceed

-if activator binding site distant from promoter then requires DNA to loop

19

What are activator proteins?

help RNA polymerase recognize the promoter region and begin transcription

-eg cAMP

20

What is global control?

single proteins that regulate the expression of multiple operons

-activate/inhibit entire sets of genes

21

How do E. coli cells choose glucose over other sugars as an energy source?

Single repressor protein, regulons, prevent transcription of group of genes to metabolize other sugars

-alot of glucose present=prevent transcription of other sugar enzymes

-not alot of glucose=allow transcirption of these enzymes

22

How do microbes sense/respond to environmental conditions?

Temperature

pH

Oxygen

Nutrients

Other microbes

23

What are the types of signal molecules that cause microbes to respond to their environment?

Internal signals

-small molecules that permeate membrane

-directly affect transcription

 

External signals

-large molecules that can't permeate membrane

-require signal transduction to affect transcription

24

What is an example of internal signals?

Quorum Sensing

-gene expression requires minimum number of bacteria to be present

-Release autoinducer signal molecules that activate transcription of genes

25

How do external signal molecules work?

Signal transduction

-external signal activates gene expression

 

Two component regulatory system

-sensor kinase protein in cytoplasmic membrane detects signal and phosphorylates response regulator

-response regulator binds DNA and represses transcription

26

How can RNA regulate gene expression?

Transcription

-attenuation

 

Translation

-riboswitches+antisense RNA

 

No regulatory proteins required

27

What is attenuation?

occurs AFTER initiation of transcription and BEFORE its completion

 

Forms alternative structures of RNA

-Form 1 = stem+loop form ahead of RNA polymerase

-transcription blocked

-Form 2 = stem+loop form behind RNA polymerase

-transcription proceeds

28

What is an example of attenuation?

tryptophan synthesis

29

What are riboswitches?

Form of RNA-based gene regulation that prevents translation

-signal metabolite binds directly to mRNA

-uses secondary mRNA structures like attenuation

 

Form 1

-shine-dalgarno unbound

-translation proceeds

 

Form 2

-shine-dalgarno bound

-translation blocked

30

What is antisense RNA?

Form of RNA-based regulation

-prevents translation where small RNA, sRNA, binds to synthesized mRNA

-makes double stranded mRNA=no translation b/c cell stops it since only viruses have dsRNA