Genetics Chapter 17 Regulation Of Gene Expression In Prokaryotes

Front 1

Proaryotes regulate gene expression in response to what?

Back 1

Environmental Conditions

Front 2

Enzymes in gene regulation may be (3 things)

Back 2

Inducible (adaptive), constitutive, and repressible

Front 3

Regulation may be under (2 things)

Back 3

Positive Control and Negative control

Front 4

Regulatory elements that are almost always located upstream of the gene cluster they control

Back 4

Cis-acting

Front 5

The molecules that bind cis-acting sites

Back 5

Trans-acting elements

Front 6

Lactose Metabolism in E. Coli is regulated by an

Back 6

Inducible System
-were the enzymes responsible for lactose metabolism are inducible and lactose is the inducer

Front 7

Has 3 strucural genes (lacZ, lacY, and lacA) with an upstream regulatory region consisting of an operator and a promoter.

Back 7

Lac operon

Front 8

The lacZ gene encodes what enzyme that converts the disaccharide lactose to the monosaccharides glucose and galactose?

Back 8

ß-galactosidase

Front 9

The lacY gene specifies the primary structure of what enzyme that facilitates the entry of lactose into the bacterial cell?

Back 9

Permease

Front 10

The lacA gene codes for what enzyme that may be involved in the removal of toxic by-products of lactose digestion from the cell?

Back 10

Transacetylase

Front 11

The structural genes of the lac operon are transcribed as a

Back 11

Polcistronic mRNA (see slide 6 for picture)

Front 12

Scientists who proposed the the operon model in which a group of genes is regulated and expressed together as a unit

Back 12

Jacob and Monod

Front 13

Why is the lac operon subject to negative control?

Back 13

Because transcription occurs only when the repressor fails to bind to the operator region. (See slides 8-10)

Front 14

The lacI gene regulates transcription of the structural genes by producing what?

Back 14

A repressor molecule

Front 15

The repressor created by the lacI is _______, meaning that it interacts reversibly with another molecule, causing both a conformation change in 3-d shape and a change in chemical activity

Back 15

Allorsteric

Front 16

What did the analysis of lac expression in the absence or presence of lactose in partial diploid merozygotes prove?

Back 16

The operon model for the lac operon (Slides 13 & 14)

Front 17

What exerts positive control over the lac operon and is involved in repressing expression of the lac operon when glucose is present?

Back 17

Catabolite-Activating Protein (CAP)

Front 18

Inhibition from the catabolite-activating protein

Back 18

Catabolite repression

Front 19

In the absence of glucose and the presence of lactose...

Back 19

CAP exerts positive control by binding the CAP-binding site and faciliatating RNA polymerase binding at the promoter (See slide 17)

Front 20

For maximal expression, the repressor must not be...
And CAP must be...

Back 20

bound at the operator
&
bound at the CAP-binding site

Front 21

What is required for CAP binding

Back 21

cyclic adenosine monophosphate (cAMP)

Front 22

Glucose represses expression of ____________, the enzyme that catalyzes the production of cAMP, and thus prevents CAP from binding when glucose is present.

Back 22

Adenylyl cyclase

Front 23

Confirmed the Operon Model

Back 23

Crystal Structure Analysis of Repressor

Front 24

A detailed structure of the lac operon and regulatory regions reveals how many sites for repressor binding? And why must all three operators be bound?

Back 24

3 sites
For maximum repression
See Slide 20

Front 25

Binding of the repressor to operators O1 and O3 creates a ________, which prevents access of RNA polymerase to the promoter.

Back 25

Repression loop

Front 26

1. The Tryptophan Operon in E. Coli is a ...
2. The enzymes for tryptophan production form an...
3. In the presence of tryptophan, the (answer to #2) is ....

Back 26

1. Repressible Gene System
2. Operon
3. Repressed

Front 27

Tryptophan functions as a _________, which is required for the repressor to bind to the operator.

Back 27

Corepressor (See slides 23-25)

Front 28

The trp structural genes are preceded by a leader sequence containing a regulatory site called an...

Back 28

Attenuator

Front 29

The mechanism by which expression of the rest of the trp operon is repressed after transcription of the leader sequence.

Back 29

Attenuation

Front 30

In the absence of tryptophan, transcription is...

Back 30

Not terminated in the leader region and proceeds through the entire operon.

Front 31

In the presence of tryptophan, the hairpin structures formed act as a transcriptional ________.

Back 31

Terminator

Front 32

In the absence of tryptophan, a different hairpin forms and acts as an __________, and transcription proceeds.

Back 32

antiterminator (Slide 30)

Front 33

Contains two tryptophan codons

Back 33

Leader region

Front 34

Forms in the abscence of tryptophan because the ribosome stalls at these codons as there is not adequate charged tRNA(trp)

Back 34

The antiterminator hairpin structure

Front 35

In the presence of tryptophan, the ribosome proceeds through this sequence and the __________ can form.

Back 35

Terminator hairpin

Front 36

The attenuation mechanism is common to several operons for enzymes responsible for synthesis of other amino acids such as...
(don't know if we'll need to know this)

Back 36

Threonine, histidine, leucine, and phenylalanine

Front 37

Instead of ribosome stalling, the mechanism of attenuation for the trp operon involves a protein called_______. It has 11 subunits, each of which can bind one molecule of tryptophan. When fully saturated, it can bind to the 5' leader sequence to form the terminator hairpin and prevent formation of the antiterminator hairpin.

Back 37

TRAP (trp RNA-binding attenuation protein)
See slide 35.

Front 38

Uncharged tRNA(trp) induces expression of the...

Back 38

anti-TRAP(AT) gene

Front 39

_________ associates with TRAP in the tryptophan-activated state and inhibits binding to the target leader RNA sequence.

Back 39

The AT protein

Front 40

The ara Operon is controlled by a regulator protein that exerts...

Back 40

...both positive and negative control

Front 41

_________ is subject to both postive and negative regulation by the _AraC_.

Back 41

Arinose (ara) operon

Front 42

_______ interacts with 2 regulatory regions: araI and araO2. It also bnds to araI in the presence of arabinose and CAP-cAMP to induce expression. In the absence of arabinose and CAP-cAMP, it binds to both araI and ara O2 to form a loop that causes repression.

Back 42

AraC (See slide 39-40)