Chapter 14 - Gene Regulation in Bacteria

Question 1

Regulatory transcription factors or RTF

Answer 1

• proteins that regulate transcription by binding to DNA
• turn on and off

Question 2

Activator

Answer 2

• Protein when bound to a cis (the same) acting regulatory DNA element, such as a promoter or an enhancer, activates transcription of an adjacent promoter (positive control)
• helps turn gene expression on

Question 3

Repressor

Answer 3

-Protein that binds to a cis-acting regulatory DNA element and prevents transcription (negative control)

Question 4

Operators

Answer 4

• DNA element at one end of an operon that is the binding site for the repressor
• binds to repressors to stop gene expression

Question 5

Operators are found only in?

Answer 5

Prokaryotes

Question 6

Allosteric Site

Answer 6

Site on a protein that binds a small molecule causing a change in the conformation of the protein that modifies the activity of its active site

Question 7

Give an example of an allosteric site

Answer 7

Glucose - changes shape therefore changes activity

Question 8

Allosteric effector

Answer 8

small molecule that binds to the allosteric site

Question 9

allosteric transition

Answer 9

change for one conformation of a protein to another

Question 10

Induction

Answer 10

relief of repression of a gene or set of genes under negative control

Question 11

Inducers

Answer 11

environmental agent that triggers transcription from an operon
- also turns on gene expression

Question 12

Bacteria are?

Answer 12

Nutritional opportunists

Question 13

What are the 3 things bacteria must do?

Answer 13

1. recognize environmental conditions in which they should be activate or repress the transcription
2. must be able to toggle on or off specific gene or groups of genes
3. have constitutive genes encode proteins that are necessary for the survival of the organism

Question 14

Genes that are unregulated are termed

Answer 14

constitutive - always on
constant levels of expression

Question 15

What two scientists were interested in the phenomenon known as the enzyme adaptation?

Answer 15

Francois Jacob and Jacques Monod

Question 16

What is the enzyme adaptation?

Answer 16

An observation that a particular enzyme appears in the cell only after the cell has been exposed to the enzyme’s substrate

Question 17

what is an operon?

Answer 17

a group of two or more genes that are under the transcriptional control of a single promoter

Question 18

Polycistronic message

Answer 18

an RNA that contains the sequence of 2 or more genes

Question 19

What are the 3 lac genes?

Answer 19

1. Permease (gene Y)
2. Beta-Galactosidase (gene Z)
3. Beta-Galactoside transacetylase (Gene A)

Question 20

What does permease do?

Answer 20

transport lactose into the cell

Question 21

what does beta galactosidase do?

Answer 21

to modify lactose into allolactose and cleave the lactose molecule to yield glucose and galactose

Question 22

Why is glucose so important?

Answer 22

Its needed to make ATP which is energy!

Question 23

What does Beta galactoside transacetylase do?

Answer 23

-Gene A is not needed for lactose metabolsim but transfers an acetyl group from acetly-Co A to beta galactosides

Question 24

Gene Z,Y,A are under the control of?

Answer 24

Lac I gene which helps coordinate expression

Question 25

When the ___ binds the repressor, the operon is fully expressed or ___.

Answer 25

- inducer - induction

Question 26

Why is the repressor important?

Answer 26

- needs to be there to shut system down if no lactose is present (no need to waste energy if lactose is not needed to convert to glucose)

Question 27

What mutation did Jacob, Monod, and Arthur Pardee identify?

Answer 27

LacI-

Question 28

Why is the LacI- a mutant gene?

Answer 28

- it does not produce a functional repressor - constitutive expression of the lac operon even in the absence of lactose (always on) - mapped very close to the lac operon

Question 29

How did Jacob and Monod figure out how the lac operon was the control?

Answer 29

used a synthetic inducer and created partial diploids

Question 30

What is the other name for partial diploids and how did they make them?

Answer 30

- Merozygote - by inserting plasmids to create a diploid (need to figure out if it was D or R) - all prokaryotes are haploid

Question 31

Cis acting means it can only affect

Answer 31

the things that are directly attached to it

Question 32

What are the 2 environmental conditions have to be met for lactose metabolites to expressed?

Answer 32

1. Lactose needs to be present 2. Glucose cannot be present (if present, why make more?)

Question 33

Glucose causes what?

Answer 33

Catabolite repression

Question 34

Describe catabolite repression

Answer 34

- lactose breaks down into glucose and galactose so the presence of glucose stops lac operon expression - done via Catabolite activator protein (CAP)

Question 35

What does the catabolite activator protein or CAP do?

Answer 35

monitors if glucose is present in the environment

Question 36

high cAMP =

Answer 36

Low glucose

Question 37

low cAMP =

Answer 37

high glucose

Question 38

What is the trp operon involved in?

Answer 38

the biosynthesis of the amino acid tryptophan

Question 39

What are the 2 levels of regulation?

Answer 39

1. Global - repressor binds 2. Attenuation - ribosome

Question 40

trpR does what

Answer 40

encodes the trp repressor protein - repression

Question 41

trpL does what?

Answer 41

- encodes a short peptide called the leader peptide -dimmer control

Question 42

Contrast the Lac vs Trp operon systems

Answer 42

Lac - utilizes the specific thing vs. Trp makes things using trp to Amino acids

Question 43

High levels of trp =

Answer 43

system shuts off

Question 44

what does the trp mRNA leader sequence contain?

Answer 44

1. attenuator region 2. two trp codons following right after another

Question 45

Why does translation stall in bacteria?

Answer 45

when trp is low it allows for transcription to proceed and the stem-loop does not form

Question 46

Formation of the stem-loop results in ___ and why?

Answer 46

- termination of transcription - the ribosome knocks off the RNA polymerase

Question 47

List the two types of gene regulation after mRNA is transcribed

Answer 47

1. translational 2. posttranslational

Question 48

what is the purpose of a translational regulatory protein ?

Answer 48

to prevent transcription from being translated (efficiency purposes)

Question 49

what proteins act to inhibit translation?

Answer 49

translational repressors to bind to mRNA

Question 50

Translational repressors inhibit translation in one of 2 ways:

Answer 50

1. Binding next to Shine-Dalgarno Sequence and/or start codon 2. Out the Shine-Dalgarno/start codon region

Question 51

Binding next to the shine-dalgarno sequence will what?

Answer 51

hinder the ribosome from initiating translation

Question 52

Binding outside the Shine-dalgarno start codon region will what?

Answer 52

stabilize an mRNA secondary structure (hair pin loops within the coding region) that prevents initiation

Question 53

Translational repression is also found in?

Answer 53

Eukaryotes

Question 54

A second way to regulate translation is?

Answer 54

synthesis of antisense RNA

Question 55

What is antisense RNA?

Answer 55

an RNA strand that is complementary to mRNA

Question 56

a common mechanism to regulate the activity of metabolic enzymes is called

Answer 56

feedback inhibition