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BIOL311 > Topic 10: Prokaryotic Gene Regulation- Lac Operon > Flashcards

Topic 10: Prokaryotic Gene Regulation- Lac Operon Flashcards

1
Q

Transcriptional regulation in bacteria is relatively simple because it

A

involves a single activator or repressor protein

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2
Q

Transcriptional regulation in eukaryotes is complex because (2)

A
  • Multiple DNA sequences and proteins are involved
  • DNA packaging with proteins in the nucleus (chromatin)
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3
Q

Prokaryote have a —- of RNA polymerase

A

single type

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4
Q

RNA polymerase

Structural

A

composed of a 5-subunit core plus a subunit called sigma factor.

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5
Q

Sigma factor

A

Positions RNA polymerase corectly at the promotor and after transcription is initiated. sigma factor leaves. Some sigma factor recognize promotors of genes required for growth in high heat while others for nitrogen saturation

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6
Q

Factor independent termination

A

GC rich DNA followed bu an A rich stretch causes RNA polymerase to release from the DNA template. Forms hairpin loop followed by bunch of UUUU mrna. Very unstable and polymerase try to stable by stoping but hairpin makes it fall off.

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7
Q

Rho dependent termination

A

Rho factor recognize a C-rich sequence of RNA and climbs up to release RNA polymerase (stopped at terminator) from the DNA template.

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8
Q

Promotor

A

DNA sequence where RNA polymerase binds to initate transcription

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9
Q

Activator

What it is

A

Protein bringing the RNA polymerase closer to the promotor

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10
Q

Repressor (2 types)

A

Protein blocking RNA polymerase from binding to the promotor or blocking it from moving along the DNA

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11
Q

Allosteric effectors

A

Small molecules that bind to the allosteric site of regulatory proteins

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12
Q

Effector binds which allows the activator to

A

Bind at the activator binding site

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13
Q

Operon (4)

What it isx2+genes+product

A
  • Linked genes under the control of a single promotor
  • Functionally related genes (ex: all involved in lactose metabolism)
  • Genes are transcribed onto a single mRNA molecule
  • Either all or none of the gene products will be synthesized
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14
Q

Lac Operon

A

Operon required for the transport and metabolism of lactose

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15
Q

Permease (Y)

A

Transports lactose into the cell

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16
Q

Beta-galactosidase (Z)

A

Modifies lactose into allolactose and cleaves lactose

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17
Q

I gene

A

encodes the repressor (Protein that can then bind to the operator)

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18
Q

Talk about the location of the I gene

A

it can be far away fro the lac operon or near, the location isnt important because only the protein that it encodes is important (free to float in cell)

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19
Q

Trans-acting

A

Affect gene expression of distant genes (on DNA other than where the trans-acting factor is encodoes)- in addition to nearby genes

Far away gene, nearby gene, gene on same DNA, on different DNA

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20
Q

Cis-acting

A

Affect gene expression of nearby genes (only genes on the sane piece of DNA as the cis-acting factor is found)

Affect nearby gene or gene on the same piece of DNA

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21
Q

Lac operon expression is regulated by both

A

negative regulation and positive regulation

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22
Q

Negative regulator

A

involves a repressor -> turning the lac operon ON/OFF

23
Q

Positive regulation

A

involves an activator -> fine tuning expression levels from the Lac operon

24
Q

Lactose is an

A

inducer(word for binding to repressors)

25
Q

P-

A

RNA plymerase cannot bind to the promotor

26
Q

Z-

A

Inactive Z

27
Q

Oc

A

Cannot bind to operator

28
Q

Constitutive mutation

A

operon is on wether the inducer is present or not

29
Q

In experiments, IPTG is

A

sometimes used as the inducer instead of Lactose

30
Q

F’ plasmids

A

F plasmids carrying bacterial genomic DNA because exiting the genomic wasn’t clean and pick up some surrounding dna

31
Q

Merozygote

+in terms of lac operon

A

partial diploid in which we have inserted a F’ plasmid in a bacterial cell
*2 copies of lac operon

32
Q

Z+ and Z-

A

Z+ is dominant over Z-

33
Q

O mutation is

A

cis acting

34
Q

I+ ad I-

A

I+ is dominant over I-

35
Q

Is and I+

A

Is is dominant over I+

36
Q

Oc is — to Is

A

epistatic (mask the effect of Is)

37
Q

If glucose is present then expression from lac operon is

A

minimal

38
Q

If there is no glucose then expression from lac operon is

A

enhanced

39
Q

Glucose levels regulate —- by

A

cAMP levels. Glucose inhibits conversion of ATP to cAMP

40
Q

cAMP is an —— as it—–

A

Allosteric effector for CAP.cAMP binds to CAP, changing its shape and making it able to bind DNA and promote transcription

41
Q

CAP

A

Binds to the CAP-binding site in the promotor when bound to cAMP. CAP-cAMP complex enhances transcription by RNA polymerase

42
Q

CAP-

A

CAP cannot bind to the promotor

43
Q

CAP+ and CAP-

A

CAP+ is dominant over CAP-

44
Q

Tryptophan

A

An amino Acid

45
Q

TRP operon is turned on when

A

Turned on when tryptophan isnt avaliable from the environment

46
Q

Order of the structural genes in the trp operon

trpA/B

A

coressponds to the order that the proteins act in the biosynthetic pathway

47
Q

Trp operon expression is regulated by (2)

A

negative regulation and attenuation (regulation after transcription has been initated)

48
Q

tryptophan binding to TrpR repressor allows

A

TrpR to bind to trpO and inhibit transcription of the 5 structural genes

49
Q

in the abscene of tryptophan, TrpR

A

cannot bind to the TrpO and the genes are transcribed

50
Q

Leader peptide can

A

terminate transcripts before the RNA polymerase reaches the first structural gene of the operon by stalling ribosome
- UGG codon for typtophan but its rare

51
Q

High tryptophan level in terms of attenuation

A

sufficient tRNAs charged with tryptophan to translate leader peptide which contains 2 Trp codons. Binding of ribosome in 4 and 3 causes mRNA conformation that favours transcription termination as there is a string of UUUU. so then the RNA pol gets stuck at the loop and unstable and falls of

52
Q

Low tryptophan level in terms of attenuation

A

Ribosome stalls at the Trp codons in the leader peptide (low tRNA). Cause region 2 and 3 to pair tgt as robsomes dont reach it. Favouts transcription.

53
Q

Factor- independent terminator +ex (2)

A
  • a mechanism of transcription termination in which RNA poly transcribes a stem loop followed by a string of U’s
    • in Trp regulation, the 3-4 ste loop is followed by a string of U’s

BIOL311 (15 decks)

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