Gene Regulation in bacteria

Question 1

Gene regulation

Answer 1

The phenomenon in which the level of gene expression can vary under different conditions

Question 2

Constitutive genes

Answer 2

Unregulated genes that have constant level of expression (ex. polymerase “house keeping genes”)

Question 3

What are a few common process that are regulated at the genetic level?

Answer 3

1. Metabolism
2. Response to environmental stress
3. Cell division

Question 4

_________ in bacteria can occur at any step in gene expression

Answer 4

Gene regulation

Question 5

In bacteria the common way to regulate gene expression is by influencing the rate at which __________ is initiated

Answer 5

Transcription

Question 6

Since gene expression is usually referred to being _______ or _______ at the level of transcription this means that the rate of RNA synthesis can be increased or decreased

Answer 6

Increased or Decreased

Question 7

What are the two regulatory proteins that are involved in transcriptional regulation?

Answer 7

1. A repressor
2. An activator

Question 8

Repressor (negative regulator)

Answer 8

A regulatory protein that binds to the DNA & stops (inhibits) transcription

Question 9

An activator (positive regulatory)

Answer 9

A regulatory protein that increased the rate of transcription

Question 10

Transcriptional regulation by a repressor is called what?

Answer 10

Negative control

Question 11

Transcriptional regulation by an activator is called what?

Answer 11

Positive control

Question 12

________ molecules play a crucial role in transcriptional regulation where they bind to an activator or repressor which causes the activator or repressor to bind to the DNA

Answer 12

Small effector molecules

Question 13

What are the types of effector molecules?

Answer 13

1. An inducer
2. A corepressor
3. An inhibitor

Question 14

An inducer

Answer 14

Is a small effector molecule that causes transcription to increase

Question 15

How does an inducer cause transcription to increase?

Answer 15

They can bind to a repressor protein & prevent it from binding to the DNA or it can bind to an activator protein & cause it to bind to the DNA

Question 16

Inducible genes

Answer 16

Genes that are regulated by inducers

Question 17

A corepressor

Answer 17

A small effector molecule that binds to a repressor which causes the repressor to bind to the DNA & decrease transcription (activates the repressor)

Question 18

An inhibitor

Answer 18

Binds to an activator protein & prevents it from binding to the DNA (inhibit the activator)

Question 19

A corepressor & inhibitor __________ transcription

Answer 19

Decrease

Question 20

Repressible genes

Answer 20

Genes that are regulated by corepressor or inhibitors

Question 21

Enzyme adaptation

Answer 21

When a particular enzyme is produced in a cell only after a cell has been exposed to the substrate for that enzyme (when a bacterium isn’t exposed to a particular substance it doesn’t make enzymes needed to metabolize that substance)

Question 22

_______ & _______ study enzyme adaptation by observing lactose metabolism in E. Coli (studying the lac operon)

Answer 22

Jacob & Monod

Question 23

The _______ encodes proteins that are involved in lactose metabolism

Answer 23

Lac operon

Question 24

An operon

Answer 24

Contains two or more genes that are transcribed from a single promoter

Question 25

An operon encodes a ____________ mRNA

Answer 25

Polycistronic mRNA

Question 26

Polycistronic mRNA

Answer 26

An mRNA that contains the sequences of two or more genes

Question 27

What is an advantage of an operon ?

Answer 27

It coordinated regulation of group genes

Question 28

Lac Operon

Answer 28

Contains a CAP site, promoter (lacP), operator site (lacO), & there protein -encoding genes which are: lacZ, lacY, & lac A, also has a terminator region

Question 29

The lacZ encodes what ?

Answer 29

An enzyme called B-galactosidase which is an enzyme that cuts lactose into galactose & glucose

Question 30

B-galactosidase also does what as a side reaction?

Answer 30

Converts lactose into allolactose (which is an inducer of the lac operon)

Question 31

The lacY gene encodes what?

Answer 31

Lactose permease- which is a membrane protein required for the active transport of lactose into the cytoplasm of the bacterium (transport lactose)

Question 32

The ______ & _______ site are short DNA segments that function in gene regulation

Answer 32

The CAP site & Operator Site

Question 33

The CAP site

Answer 33

Is a DNA sequence that is recognized by an activator

Question 34

The operator site (operator)

Answer 34

Is a sequence of bases that provide a binding site for a repressor (bound by lacl & goes through negative regulation)

Question 35

\_\_\_\_\_\_\_ is bound by RNA polymerase

Answer 35

Promoter

Question 36

\_\_\_\_\_\_\_ is a repressor that inhibits RNA polymerase (Its not located in the operon but outside it (right before it))

Answer 36

lacl

Question 37

The ______ isn't part of the lac operon & it has it's own promoter, the i promoter

Answer 37

lacl

Question 38

The ______ encodes the lac repressor

Answer 38

lacl

Question 39

The ________ can be regulated by the lac repressor under negative control

Answer 39

Lac Operon

Question 40

When __________ is absent then the lac repressors binds to the operator site & prevents RNA polymerase from transcribing the lacZ, lacY, & lacA, genes

Answer 40

Allolactose

Question 41

When _______ is available it can bind to the lac repressor & prevent it from binding to the operator site & allow RNA polymerase to bind & transcribe lacZ, lacY, & lacA genes

Answer 41

Allolactose (is an inducer)

Question 42

Even though when the ________ binds to the operator site & inhibits transcription it doesn't completely inhibit transcription instead there is basal transcription occurring when low levels of B-galalctosidase, lactose permease, & transacetylase

Answer 42

lac repressor

Question 43

The __________ doesn't completely inhibit the lac operon because it still detect if lactose is present so that when lactose is present B-galactosidase can convert it into allolactose & remove the repressor

Answer 43

lac repressor

Question 44

Describe the first 2 steps in the cycle of lac operon induction & repression

Answer 44

1. When lactose becomes available a small amount is take up & converted to allolactose by B-galalactosidase. The allolactose binds to the repressor causing the repressor to fall off the operator site 2. lac operon proteins are synthesis. this promotes the efficient uptake & metabolism of lactose

Question 45

Describe the last 2 steps in the cycle of lac operon induction & repression

Answer 45

3. The lactose is depleted. Allolactose levels in decrease and allolactose is released from the repressor, allowing it to bind to the operator site 4. Most proteins involved with lactose ulitization are degraded

Question 46

The mutant strain _______ results in constitutive expression (constant expression) of the lac operon whether lactose is presence or absent

Answer 46

lacl^-

Question 47

The ______ results in expression of the operon even when lactose is absent because the loss-of-function mutation in the lacl gene prevents the lac repressor from binding to the lac operator site & inhibiting transcription

Answer 47

lacl^-

Question 48

Merozygote strain

Answer 48

Contains the lacl^- mutant strain on the chromosome & a normal lacl gene on the plasmid

Question 49

What are the two hypotheses for lacl function?

Answer 49

1. lacl is a repressor that is active without lactose & lacl^- mutant is an inactive repressor (to yield constitutive operon)(Hypothesis 1) 2. lacl is an activator that is inactive without lactose & lacl^- mutant is a constitutive activator (constitutive operon) (hypothesis 2)

Question 50

In catabolite repression when only lactose is present, cAMP levels are ______ & the cAMP binds to CAP site. A domain in the CAP interacts with RNA polymerase which cause it to bind to the promoter. In the presence of lactose, the lac repressor is not bound to the operator site is transcription can occur at a ______ rate

Answer 50

High, high

Question 51

In catabolite repression in the absence of both lactose & glucose, cAMP levels are _____ but the binding of the lac repressor inhibits transcription even though CAP is bound to the DNA so therefore the transcription rate is \_\_\_\_\_\_

Answer 51

High, low

Question 52

The presence of lactose in catabolite repression causes the lac repressor to be inactive which prevents it from binding to the operator site. However when glucose is presence decreases cAMP levels so its released from CAP which causes CAP not to bind to CAP site so the transcription of the lac operon is _______ when both sugars are present

Answer 52

Low

Question 53

When only glucose is presence in catabolite repression the transcription of the lac operon is _______ because the lac repressor is bound to the operator site & CAP is not bound to the CAP site

Answer 53

Low

Question 54

CAP is an \_\_\_\_\_\_\_

Answer 54

Activator

Question 55

cAMP is an \_\_\_\_\_\_\_\_

Answer 55

Inducer