Microbiology Chapter 12

Front 1

Define Transcription

Back 1

The process in which single-stranded RNA with a base sequence complementary to the template strand of DNA or RNA is made.

Front 2

What are the 3 classes of RNA formed? What are their Fxn's?

Back 2

rRNA-components of Ribosomes
mRNA-bears the message for protein synthesis
tRNA-carries AA during protein systhesis

Front 3

By what mechanism are rRNA components made in equimolar amounts? Are the transcripts of tRNA and rRNA genes processed in any way?

Back 3

?

Front 4

What enzyme is responsible for transcription in prokaryotes?Eukaryotes?

Back 4

RNA Polymerase

Front 5

What are the components of the pro. holoenzyme(5) and apoenzyme(core enzyme)(4)?

Back 5

holo-2α,β,β’,σ
core-α,β,β’

Front 6

What is the Direction of the enzymes activity?

Back 6

5' to 3'

Front 7

(RNA Poly)What is the promoter? What are two elements of the prok. promoter?Euk?

Back 7

Prok-Pribnow box=TATAAT. σ specific (TTGACA). σ falls off afterward.
Euk-TATA box(Goldberg-Hogness): bends DNA to make it more accessable. Enchancer sites at 50 to 500

Front 8

What component of the prok RNA polymerase recognizes the promoter?How does the use of different sigma factors affect the repertoire of genes being expressed in the cell?

Back 8

Sigma factors needed to start (recognizes promoter for transcription), then falls off. ?

Front 9

What is constitutive gene expression?What factors determine the rate of expression for these genes?

Back 9

Rate determined by -35 and Pribnow consensus. The closer to consensus the more often transcribed. Never regulated. 10,000 fold diff in constitutive expression. Sigma factors determine gene expression

Front 10

What are the componenets of rho dependent and independent terminators?

Back 10

rho independant-GC rich hairpin loop. Poly U-rich sequence(weakest bonding w/ U)
rho dependent-GC rich hairpin loop proceeded by rho factor binding sites.

Front 11

Describe the conversion of hnRNA to mRNA.

Back 11

only in euk, post-transcriptional modification: 5' cap, poly-A tail, splicing of exons and introns

Front 12

What are ribozymes?

Back 12

Self-splicing RNA

Front 13

What are exons and introns?

Back 13

Introns removed by RNA splicing

Front 14

How can the same sequence encode different proteins (not in book)?

Back 14

Redundancy of AA table

Front 15

Why is euk mRNA more stable than prok. mRNA?

Back 15

?

Front 16

Define translation (where does it take place in Prok/Euk)

Back 16

Protein systhesis. the process by which the genetic message carried by mRNA directly copied from DNA codes for protiens. takes place in the cyto

Front 17

codon, anticodon, sense and nonsense codons

Back 17

Seq. of 3 nucleotides in mRNA that directs the incorporation of an AA; The base triplet on tRNA that is complimentary to mRNA; direct AA incorporation into protein; stop codons

Front 18

What is the role of the shine-dalgarno sequence?What constituent of the ribosome recognizes it?How?

Back 18

Shine-Dalgarno=ribosome binding site in prok. fpr translation start. First thing to be transcribed.
Met with the AUG

Front 19

What is the most common codon for the initiation of translation? How is translation stopped?

Back 19

AUG; UGA,UAG,UAA

Front 20

What is meant by tRNA charging?

Back 20

binds ATP and the cognate amino acid

Front 21

What are molecular chaperones? What induces their increased production? What are their fxns?

Back 21

Proteins found in all cells which fold newly formed proteins & partially denatured proteins.They are increased in concentration under high temps.,metabolic poisens, and other stressful conditions.

Front 22

What are inteins and exteins?

Back 22

Exteins are flanking regions which are not spliced out in protien splicing.
Interins are intervening regions which are removed.

Front 23

Can you explain the diauxic growth curve of E. coli growing in glu and lac?

Back 23

glu prevents use of lactose. glu used in lap period, when its used up you enter the lag period in which lac is used.

Front 24

In E.coli, CAP is an activator for operons involved in the catabolism of sugars in addition lactose. Would you expect these operons to show catabolite repression? Would you expect these operons to be inducible?

Back 24

?

Front 25

What is the DNA-binding regulatory molecule in negative control of operons (induction/repression)?

Back 25

regulatory proteins-repressors bind to operator near promoter which decrease the ability of RNA Poly to bind or leave the promoter and decrease transcription.

Front 26

What site does a repressor bind? What site is this located near?

Back 26

The repressor binds to operator near promoter.

Front 27

Define corepressor and inducer. How do they differ?

Back 27

Corepressor activates repressor gene and inturn decreases transcription.
Inducer inactivates repressor and inturn increases transcription.

Front 28

What is the DNA-binding regulatory molecule in positive control of operons? What is done in Euk. systems(from lecture)?

Back 28

Prok-activators
Euk-transcription factors bind at enhancers

Front 29

What are the roles of CAP, cAMP, and glucose in the positive regulation of the lac operon? Why does the operon require positive control (activation)?

Back 29

CAP-activator; cAMP-determines CAP binding to Plac;Glu-none then EIIBglu is phosphorylated and turns on cAMP

Front 30

Is the repressor normally active or inactive for inducible genes? Repressible genes?

Back 30

Inactivates repressor(transcription rises); activates repressor(transcription decreases).

Front 31

Is there a specific DNA-binding regulatory protein in attenuation? What is the attenuator?

Back 31

Common in AA anabolic pw. Involves the conditional termination of transcription before the 1st structural genes. Attenuator looks like a terminator. On trp operon.

Front 32

Using sections 1,2,3 and 4 of the trp operon:what is the effect of no translation? Where is there a high freq. of tryp codons? What pairs form if there is lots of tryptophane?

Back 32

no translation-then 1:2 and 3:4(termination); high then ribosome stalls @UAG and stops 2:3 allows 3:4(termination);if low then ribosome stalls in 1 2:3 and no 3:4 polymerase moves through operon (no termination)

Front 33

What are regulons and stimulons?

Back 33

collection of operons controlled by the same regulatory molecule;a collection of operons responding to the same ennironmental stimulus.

Front 34

How do sigma factors affect the process of sporulation in Bacillus subtilis?

Back 34

?global regulatory systems controlled by sigma factors

Front 35

What is meant by antisense RNA?How can it regulate gene expression at the level of translation?

Back 35

Base sequence complementary to a segment of another RNA molecule and specifically binds to another RNA molecule. Binding can block DNA replication, mRNA synthesis, or translation.

Front 36

What are the components of a two-component regulatory system? What do each of these molecules do?

Back 36

Two-component pphosphorelay system:signal transduction involving transfer of phosphoryl grp. Sensor kinase-"senses" environment and phosphorylates other molecules.
Response regulator-changes activity with phosphorylation.

Front 37

How does replication affect cell divison? How can a cell that requires 40' to replocate its DNA divide every 20?

Back 37

Inhibition of replication stops septation.
-two forks can be used to divide faster.

Front 38

Can you identify the regularoty elements in the neg. control of the lac and trp operons?

Back 38

lac-w/ glu lactose is not used. (lac operon is inducible with lac as inducer)Repressor binds operator.(O) 3' of P
trp:repressible;trp operon=P,O,and structural genes that code for tryptophan(corepressor).trpR binds O only in presence of typtophan

Front 39

What is the DNA-binding regulatory molecule in positive control of operons?

Back 39

The DNA-binding regulatory molecule in positive contorl of operons is catabolite activator protein (CAP)

Front 40

What is done in eukaryotic systems (in lecture)?

Back 40

???

Front 41

What are the roles of CAP, cAMP, and glucose in the positive regulation of the lac operon?

Back 41

CAP binds to the CAP site on the promoter when complexed with cAMP; this binding allows RNA polymerase to bind to the promoter and begin transcription. Glucose???

Front 42

Why does the operon require positive control (activation)?

Back 42

The operon requires positive control (activation) to upregulate mRNA synthesis (???)

Front 43

Is there a specific DNA-binding regulatory protein in attenuation?

Back 43

No, there is not a specific DNA-binding regulatory protein in attenuation.

Front 44

What is the attenuator?

Back 44

The attenuator is a rho-independent termination site in the leader sequence that is involved in attenuation.

Front 45

Using sections 1,2,3, and 4 of the trp operon: a) What is the effect of no translation?

Back 45

If there is not translation of the mRNA after the RNA polymerase has begun copying the leader region, segments 3 & 4 form a hairpin loop, and transcription terminates before the poymerase reaches the trpE gene (RNA poly dissociates)

Front 46

Using sections 1,2,3, and 4 of the trp operon: b) Where is there a high frequency of trp codons?

Back 46

There is a high frequency of trp codons in the leader peptide sequenc (section 1).

Front 47

Using sections 1,2,3, and 4 of the trp operon: c) What pairs form if there is lots of tryptophan?

Back 47

(short answer: 3 & 4) If there is lots of tryptophan, the ribosome synthesizes the leader peptide and stops at terminator codon between sections 1 & 2; the ribosome pauses & prevents 2 from pairing w/3; segments 3 & 4 form a hairpin loop, and the RNA polymerase terminates at the attenuator just as if no translation had taken place.

Front 48

What are regulons and stimulons?

Back 48

A regulon is a collection of operons controlled by the same regulatory molecule. A stimulon i sa collection of operons responding to the same environmental stimulus.