T3M2 Flashcards

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1
Q

Operon end goal

A

the ability to express genes together, expressed as one big long mRNA sequence (polycistronic)

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2
Q

Polycistronic mRNA

A

a molecule that contains more than one protein encoding segment

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3
Q

Lactose operon is negatively regulated - negative cue

A

glucose is in the environment

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4
Q

cAMP levels will be ____ when glucose levels are high

A

low

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5
Q

What is cAMP?

A

a signaling molecule, more positive regulation of the lac operon, enhance gene operation, made from ATP

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6
Q

When glucose levels are low cAMP levels will be

A

high

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7
Q

CRP-cyclic AMP complex facilitates

A

the ability of RNA polymerase to bind to the lac promoter

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8
Q

More cAMP=

A

more positive regulation and less glucose!!

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9
Q

High glucose=

A

less cAMP, not binding as much to enhancer site

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10
Q

Is the lac operon ever fully off?

A

No, if it was fully off, 0 lac permease, run out of glucose and there is no cue for lactose to get in.

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11
Q

As E. coli cells transition from glucose to lactose
metabolism, there is a concomitant increase in

A

the amount of detectable beta-galactosidase and lactose permease proteins

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12
Q

beta-galactosidase and lactose permease proteins are not expressed until

A

glucose is fully depleted from the growth medium

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13
Q

lactose permease is

A

a transport protein that sits in the bacterial cell membrane and allows for the transport of lactose into the bacterial cells

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14
Q

The beta-galactosidase protein is

A

the cytoplasmically situated bacterial enzyme that cleaves the imported lactose into glucose and galactose

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15
Q

A key advantage to the organization of the prokaryotic genome is

A

groups of related genes with similar functions
can often be found clustered together into
operons - ability to control the transcription of the whole gene cluster as one unit

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16
Q

Each gene has its own promoter and enhancers

A

eukaryotes

17
Q

Model for prokaryotic gene expression discovered by

A

Francois Jacob and Jacques Monod (1961)

18
Q

In bacteria, groups of functionally related genes are organized into

A

transcriptional units along the bacterial
chromosome

19
Q

Bacteria, gene clusters are controlled by

A

a single on/off switch that can control the transcription of the clustered genes mediated by an operon

20
Q

The bacterial operon consists of

A

a promoter, an operator (or on-off switch), and the coordinated gene cluster whose products will function in a common pathway or cellular response

21
Q

An operator is

A

a sequence of nucleotides near the start of the operon that can be regulated to allow or inhibit transcription

22
Q

When the operator is not bound to any
transcriptional inhibitor

A

RNA polymerase can attach to the promoter and transcribe the genes in the operon

23
Q

transcription in bacteria can give rise to

A

one long mRNA molecule (or polycistronic mRNA) that can code for many protein

24
Q

During translation, bacterial cells can then produce separate polypeptides because

A

the polycistronic mRNA is punctuated with start and stop codons that signal where the coding sequence for each polypeptide begins and ends

25
Q

The lac operon is

A

a model for transcriptional regulation in prokaryotes

26
Q

The regulation of beta-galactosidase and lactose permease expression is under the control of

A

The lac operon in E. coli cells

27
Q

Regulatory sequences of transcription that exist within the lac operon

A
  • The promoter that binds the RNA polymerase
    complex
  • The operator (lacO) which is the binding site for a repressor protein that is expressed by the lacI coding sequence
28
Q

Two main structural genes
code for the primary proteins that are needed to facilitate lactose metabolism

A
  • The lacY gene which codes for a lactose permease transport protein which will embed itself in the cell membrane and allow for the import of lactose into the bacterial cell
  • The lacZ gene which codes for B-galactosidase that will be able to cleave the disaccharide lactose into glucose and galactose
29
Q

RNA polymerase can simply bind to and
activate

A

The transcription of the lacZ and lacY
genes

30
Q

the lac l gene controls

A

the expression of the lacZ and lacY genes

31
Q

lacl is the gene that codes for

A

a repressor protein which can bind to the operator and inhibit transcription from occurring

32
Q

The ability of a repressor protein to halt transcription in this manner is often identified as

A

negative transcriptional regulation

33
Q

Negatively regulated transcription process

A

a repressor protein will bind to the operator region of the operon, and this will result in turning off transcription since the RNA polymerase is no longer able to bind to the promoter region of the operon

34
Q

Lactose operon regulation

A

negative

35
Q

The lac operon repressor once expressed by the
lac l gene is able to inhibit

A

the expression of the beta-galactosidase and the lactose permease proteins

36
Q

Indicator for the general nutritional state of
E. coli cells

A

concentration of cAMP in the bacterial cell

37
Q

When glucose levels are high in the environment surrounding bacterial cells, there is

A

an inhibition of the enzyme adenylyl cyclase,
which catalyzes the production of cAMP from
ATP (low levels of intracellular
cAMP)

38
Q

High extracellular glucose concentration

A
  • inhibition on adenylyl cyclase enzyme
  • low levels cAMP
  • CRP-cAMP complex will not bind lac operon
  • lower levels of transcription
39
Q

What can bind to repressor proteins and prevent their binding to the DNA?

A

Inducer proteins