Gene Regulation

Question 1

is a label for the cellular processes that control the rate and manner of gene expression.

Answer 1

gene regulation

Question 2

Some genes are expressed ___, as they produce proteins involved in basic metabolic functions;

Answer 2

continuously/constitutively

Question 3

some genes are expressed as part of the process of ___ ___

Answer 3

cell differentiation

Question 4

(whether and how much a gene is transcribed into mRNA)

Answer 4

transcriptional control

Question 5

(whether and how much an mRNA is translated into protein)

Answer 5

translational control

Question 6

(whether the protein is in an active or inactive form, and whether the protein is stable or degraded)

Answer 6

post translational control

Question 7

mechanisms of gene regulation include (3)

Answer 7

transcriptinal control
translational control
post translational control

Question 8

In prokaryotic organisms such as bacteria and archaea, structural proteins with related functions are usually encoded together within the genome in a block called an

Answer 8

operon

Question 9

In prokaryotic organisms such as bacteria and archaea, structural proteins with related functions are usually encoded together within the genome in a block called an operon and are transcribed together under the control of a single

Answer 9

promoter

Question 10

this forms a polycistronic transcript (mRNA that encodes several proteins). T

Answer 10

transcription of structural genes

Question 11

each operon includes DNA sequences that influence its own transcription; these are located in a region called the

Answer 11

regulatory region

Question 12

The regulatory region includes the promoter and the region surrounding the promoter, to which ___ factors, proteins encoded by regulatory genes, can bind.

Answer 12

transcription

Question 13

Transcription factors influence the binding of __ ___ to the promoter and allow its progression to transcribe structural genes.

Answer 13

RNA polymerase

Question 14

is a transcription factor that suppresses transcription of a gene in response to an external stimulus by binding to a DNA sequence within the regulatory region called the operator

Answer 14

repressor

Question 15

A repressor is a transcription factor that suppresses transcription of a gene in response to an external stimulus by binding to a DNA sequence within the regulatory region called the

Answer 15

operator

Question 16

which is located between the RNA polymerase binding site of the promoter and the transcriptional start site of the first structural gene

Answer 16

operator

Question 17

___ binding physically blocks RNA polymerase from transcribing structural genes.

Answer 17

repressor

Question 18

is a transcription factor that increases the transcription of a gene in response to an external stimulus by facilitating RNA polymerase binding to the promoter.

Answer 18

activator

Question 19

a third type of regulatory molecule, is a small molecule that either activates or represses transcription by interacting with a repressor or an activator.

Answer 19

inducer

Question 20

Prokaryotic operons are commonly controlled by the binding of repressors to operator regions, thereby preventing the transcription of the structural genes. Such operons are classified as either __ operons or ___ operons.

Answer 20

repressible
inducible

Question 21

typically contain genes encoding enzymes required for a biosynthetic pathway. As long as the product of the pathway, like tryptophan, continues to be required by the cell, a repressible operon will continue to be expressed.

Answer 21

repressible operons

Question 22

However, when the product of the biosynthetic pathway begins to accumulate in the cell, removing the need for the cell to continue to make more, the expression of the operon is repressed.

what kind of operon??

Answer 22

repressible operon

Question 23

often contain genes encoding enzymes in a pathway involved in the metabolism of a specific substrate like lactose. These enzymes are only required when that substrate is available, thus expression of the operons is typically induced only in the presence of the substrate.

Answer 23

inducible operons

Question 24

The E. coli lactose or lac operon consists of what gene

Answer 24

regulatory (i) gene
promoter (p) gene
operator (o) gene
structural genes (z,y,a)

Question 25

is the site where RNA polymerase binds together with cyclic adenosine monophosphate receptor protein complex (or cAMP-CRP complex) to start transcription of the z, y, a genes

Answer 25

p gene

Question 26

The p gene is the site where RNA polymerase binds together with what complex

Answer 26

cAMP-CRP complex

Question 27

cAMP-CRP complex

Answer 27

cyclic adenosine monophosphate receptor protein complex

Question 28

code for B-galactosidase

Answer 28

Lac Z

Question 29

which digests lactose into its two constituent sugars: glucose and galactose

Answer 29

B-galactosidase

Question 30

Lac Y codes for __ that helps to transfer lactose into the cell

Answer 30

lac permease

Question 31

Lac A codes for ___the relevance of which in lactose metabolism is not entirely clear

Answer 31

trans-acetylase

Question 32

is responsible for coding the polypeptide chain, four copies of which form an aggregate called the repressor protein.

Answer 32

Lac I gene

Question 33

The i gene is responsible for coding the polypeptide chain, __ copies of which form an aggregate called the repressor protein.

Answer 33

four

Question 34

The i gene is responsible for coding the polypeptide chain, four copies of which form an aggregate called the ___ protein.

Answer 34

repressor

Question 35

The active repressor binds to the operator and consequently, the RNA polymerase cannot transcribe the structural gene. is lactose present?

Answer 35

no

Question 36

The operon is thus repressed or “turned off” in the absence of environmental signals. is lactose present?

Answer 36

no

Question 37

Induction of the operon occurs when the disaccharide ___ is provided to the E. coli which needs to break it down for energy release.

Answer 37

lactose

Question 38

The lactose gains entry into the cell by binding to ___ coded for by the lac y gene

Answer 38

permease

Question 39

acts on lactose and breaks it down to galactose and glucose.

Answer 39

B-galactosidase

Question 40

It also catalyzes the conversion of lactose to allolactose which acts as an inducer, binding strongly to the repressor, such that repressor is distorted and removed from the lac o gene.

Answer 40

B-galactosidase

Question 41

This opens the operator, giving the RNA polymerase access to the promoter and thereby transcribing the structural genes which in turn continue to produce the proteins that would facilitate the metabolism breakdown of ___ for the cell’s energy needs until it is consumed.

Answer 41

lactose

Question 42

when lactose is __, the lac repressor binds tightly to the operator. it gets in the RNA polymerase's way, preventing transcription

Answer 42

absent

Question 43

when lacotse is ___, allolactose binds to the lac repressor and makes it let go of the operator. RNA polymerase can now transcribe the operon

Answer 43

presentg

Question 44

Bacteria typically have the ability to use a variety of substrates as ___ sources.

Answer 44

carbon

Question 45

is usually preferable to other substrates, bacteria have mechanisms to ensure that alternative substrates are only used when this has been depleted.

Answer 45

glucose

Question 46

Additionally, bacteria have mechanisms to ensure that the genes encoding enzymes for using alternative substrates are expressed only when the alternative substrate is ___.

Answer 46

available

Question 47

was the first to demonstrate the preference for certain substrates over others through his studies of E. coli’s growth when cultured in the presence of two different substrates simultaneously.

Answer 47

Jacques Monod

Question 48

The ability to switch from glucose use to another substrate like lactose is a consequence of the activity of an enzyme called

Answer 48

enzyme IIA (EIIA)

Question 49

When glucose levels drop, cells produce less ATP from catabolism, and EIIA becomes ___.

Answer 49

phosphorylated

Question 50

Phosphorylated EIIA activates

Answer 50

adenyly cylclase

Question 51

an enzyme that converts some of the remaining ATP to cyclic AMP (cAMP)

Answer 51

adenyly cyclase

Question 52

yclic derivative of AMP and important signaling molecule involved in glucose and energy metabolism in E. coli.

Answer 52

cyclic AMP

Question 53

The lac operon also plays a role in this switch from using glucose to using lactose. When glucose is scarce, the accumulating cAMP caused by increased adenylyl cyclase activity binds to

Answer 53

catabolite activator protein (CAP)

Question 54

The complex binds to the promoter region of the lac operon.

Answer 54

cAMP-CAP complex

Question 55

Binding of the CAP-cAMP complex to this site increases the binding ability of RNA polymerase to the promoter region to initiate the transcription of the structural genes.

Answer 55

CAP binding site

Question 56

Thus, in the case of the lac operon, for transcription to occur, lactose must be present (removing the lac __ protein) and glucose levels must be depleted (allowing binding of an activating protein).

Answer 56

repressor

Question 57

Thus, in the case of the lac operon, for transcription to occur, lactose must be present (removing the lac repressor protein) and glucose levels must be depleted (allowing binding of an ___ protein).

Answer 57

activating

Question 58

When glucose levels are high, there is ___ repression of operons encoding enzymes for the metabolism of alternative substrates.

Answer 58

catabolite

Question 59

This operon codes for enzymes needed in the biosynthesis of tryptophan

Answer 59

trp operon

Question 60

When environmental tryptophan is ___, the operon is turned on

Answer 60

low

Question 61

This means that transcription is initiated, the genes are expressed, and tryptophan is synthesized. is trp operon on?

Answer 61

yes

Question 62

However, if tryptophan is present in the environment, the trp operon is turned ___.

Answer 62

off

Question 63

When tryptophan is not present in the cell, the repressor by itself does not bind to the operator; therefore, the operon is ___ and tryptophan is ___.

Answer 63

active synthesized

Question 64

However, when tryptophan accumulates in the cell, __ tryptophan molecules bind to the trp repressor molecule, which changes its shape, allowing it to bind to the trp operator.

Answer 64

two

Question 65

is a mechanism for reducing expression of the trp operon when levels of tryptophan are high.

Answer 65

attenuation

Question 66

prevents completion of transcription.

Answer 66

attenuatio

Question 67

When levels of tryptophan are high, attenuation causes ___ ___ to stop prematurely when it's transcribing the trp operon.

Answer 67

RNA polymerase

Question 68

is where the secondary structures are formed in the mRNA that are responsible for this premature termination. T

Answer 68

trpL and trp attenuator

Question 69

he formation of such secondary structures comes from the transcription stop signals—an inverted repeat and a string of 8 __pairs in the attenuator.

Answer 69

A-T

Question 70

Thus, __ imposes an extra level of control on an operon, over and above the repressor-operator system.

Answer 70

attenuation

Question 71

slow translation of domain 1 peptide what level of trp?

Answer 71

low

Question 72

fast translation of domain 1 peptide what level of trp?

Answer 72

high tryptophan levels

Question 73

what level of trp? domain 2-3 pairing occurs

Answer 73

low tryptophan levels

Question 74

what level of trp? domain 2 blocked by ribosome

Answer 74

high tryptophan

Question 75

what level of trp? domain 3-4 pairing occurs

Answer 75

high trp levels

Question 76

what level of trp? normal full gene transcription

Answer 76

low trp levels

Question 77

what level of trp? attenuation of transcription occurs

Answer 77

high

Question 78

what level of trp? only 10% of normal mRNAs made

Answer 78

high trp