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Microbiology > Microbial Transcription and Translation > Flashcards

Microbial Transcription and Translation Flashcards

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1
Q

RNA polymerase in prokaryotes is comprised of what two parts?

A

Core + sigma factors

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2
Q

Sigma factors

A

Proteins of RNA polymerase that direct the core to promoters

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3
Q

Two examples of sigma factors and their functions

A

Sigma 70: housekeeping

Sigma S: activated during stationary phase

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4
Q

What is the antibiotic that targets bacterial RNA polymerase?

A

Rifampin

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5
Q

Transcription generates what 3 types of RNA?

A

tRNA (transfer RNA)
rRNA (ribosomal RNA)
mRNA (messenger RNA)

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6
Q

tRNA function

A

Carries amino acids during protein synthesis

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7
Q

rRNA function

A

Component of ribosomes

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8
Q

mRNA

A

Template for protein synthesis

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9
Q

RNA uses what type of sugar instead of deoxyribose (used in DNA)?

A

Ribose

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10
Q

What base replaces thymine in RNA?

A

Uracil

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11
Q

Is RNA usually single stranded or double stranded?

A

Single stranded

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12
Q

Promoter region of DNA consists of what 3 sites?

A

+1

  • 10
  • 35
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13
Q

+1 site

A

Promoter site where transcription is started

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14
Q

-10 site

A

Promoter site where RNA polymerase binds

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15
Q

-35 site

A

Promoter site that RNA polymerase initially recognizes

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16
Q

What is the name of the DNA strand that directs synthesis of RNA? What is the name for the other strand?

A

Template strand directs RNA synthesis

Coding strand is other strand

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17
Q

Terminator

A

Sequence of DNA that signals RNA polymerase to stop transcription

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18
Q

Start codon

A

Portion of mRNA that signals beginning of translation

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19
Q

Stop codon

A

Portion of mRNA that signals ending of translation

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20
Q

Shine-Dalgarno sequence

A

Portion of mRNA that aligns ribosome with RNA for translation

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21
Q

What enzyme opens and unwinds DNA in transcription? Does it require a primer?

A

RNA polymerase

Doesn’t require a primer

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22
Q

In what direction does RNA polymerase move along the template strand? In what direction is mRNA synthesized?

A

RNA polymerase moves from 3’ to 5’

mRNA is synthesized from 5’ to 3’

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23
Q

When does the sigma factor leave RNA polymerase?

A

After transcription is initiated

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24
Q

Two types of terminators

A

Rho-independent

Rho-dependent

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25
Q

Rho-independent terminator: what structure does it encode, what does it do

A

Encodes RNA stem loop structure

Causes RNA Pol release

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26
Q

Rho-dependent terminator: what does it do, what does Rho protein do

A

Causes RNA Pol to pause

Rho binds RNA then moves towards RNA Pol, causing it to release

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27
Q

Bacteria use two-component signal transduction systems to control what in response to what?

A

Gene transcription

Environment

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28
Q

What are the two components of two-component signal transduction systems?

A

Sensor kinase + kinase domain

Response regulator

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29
Q

Sensor kinase: where is it located, what does it do

A

Part is embedded in plasma membrane, other part is inside of cell
Can sense different environmental conditions such as temperature

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30
Q

Kinase domain: what is it connected to, where is it located, what does it do

A

Connected to sensor kinase in cytoplasm

Autophosphorylates at conserved histidine using ATP in response to certain environmental conditions

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31
Q

Response regulator: what is transferred onto it and at what amino acid, what does it do when phosphorylated

A

Phosphate from sensor is transferred onto aspartate of response regulator
When phosphorylated, binds to promoter region of gene, activating transcription

32
Q

In eukaryotes, where does transcription occur?

A

Nucleus

33
Q

In eukaryotes, how many RNA polymerases are used?

A

3

34
Q

Instead of sigma factors, what do eukaryotes use for transcription?

A

Transcription factors

35
Q

TATA box

A

Promoter element of transcription in eukaryotes

36
Q

What process occurs in eukaryotes to remove introns?

A

RNA splicing

37
Q

In eukaryotes, what is done with mRNA that is not commonly done in prokaryotes?

A

Modification

38
Q

Capping

A

Modification of mRNA in eukaryotes

Methylguanosine is added at 5’ end

39
Q

Polyadenylation

A

Modification of mRNA in eukaryotes

Adenine nucleotides are added at 3’ end (tail)

40
Q

Purpose of capping and polyadenylation in eukaryotes

A

Stability of mRNA

Involvement in translation initiation

41
Q

Translation has what 2 requirements?

A

Ribosomes

Energy (GTP and ATP)

42
Q

2 subunits of bacterial ribosome

A

30S

50S

43
Q

30S subunit of bacterial ribosome: how many proteins? What rRNA?

A

21 proteins

16S rRNA

44
Q

50S subunit of bacterial ribosome: how many proteins? What rRNAs?

A

34 proteins

23S and 5S rRNA

45
Q

23S rRNA has what type of activity?

A

Enzymatic

46
Q

Ribozyme

A

RNA with enzymatic activity

47
Q

Peptidyltransferase: what rRNA, what does it do

A

Utilized by 23S rRNA to catalyze peptide bonds between adjacent amino acids

48
Q

16S rRNA: function, sequence is complementary to what mRNA sequence

A

Aligns mRNA with ribosome

Sequence is complementary to Shine-Dalgarno sequence

49
Q

Codon features how many nucleotides?

A

3 (triplet)

50
Q

How many codons total?

A

64

51
Q

How many codons specify amino acids?

A

61

52
Q

Difference between sense and nonsense codons

A

Sense codons code for amino acids, but nonsense codons trigger cessation of translation

53
Q

How many codons are stop codons? Stop codons are also referred to as what?

A

3

Nonsense codons

54
Q

Degeneracy of codons

A

Multiple codons can encode the same amino acid

55
Q

What is the start codon’s sequence? What does it code for?

A

AUG

Codes for methionine

56
Q

What are the 3 stop codons?

A

UAA
UAG
UGA

57
Q

tRNA molecule: what shape?

A

Clover leaf

58
Q

2 functional regions of tRNA

A

3’ end

Anticodon

59
Q

3’ end of tRNA: what enzyme attaches what here?

A

Synthetase enzyme attaches an amino acid here

60
Q

Anticodon: complementary to what, what does this enable it to do

A

Complementary to corresponding codon in mRNA

Enables it to hydrogen bond to mRNA codon

61
Q

Translation occurs at what organelle?

A

Ribosome

62
Q

3 stages of translation

A

Initiation
Elongation
Termination

63
Q

30S subunit contains what 3 sites?

A

A, P, E

64
Q

A site of 30S subunit: what does it stand for, what does it do

A

Acceptor/aminoacyl site

Accepts tRNA

65
Q

P site of 30S subunit: what does it stand for, what does it do

A

Peptidyl site

tRNA binds to mRNA

66
Q

E site of 30S subunit: what does it stand for, what does it do

A

Exit site

tRNA leaves ribosome from here

67
Q

Start codon in translation: first __-____

A

f-Met (formylmethionine)

68
Q

Step 1 of translation inititation

A

16S rRNA in the ribosome hybridizes with Shine-Dalgarno sequence of mRNA, aligning mRNA with ribosome

69
Q

Step 2 of translation initiation

A

tRNA with formylmethionine binds to the start codon in the P site

70
Q

Step 1 of translation elongation

A

Next tRNA plus amino acid binds to A cite

71
Q

Designation for tRNA + amino acid

A

Charged

72
Q

Insertion of tRNA into A site requires what?

A

GTP

73
Q

Step 2 of translation elongation

A

Peptide bonding joins amino acids, catalyzed by 23S rRNA

74
Q

Step 3 of translation elongation

A

Ribosome moves 1 codon along mRNA

75
Q

Step 4 of translation elongation

A

Empty tRNA moves from P to E site

76
Q

Translation termination: what two things happen?

A
  1. Any one of 3 stop codons (UAA, UAG, or UGA) is reached

2. Release factors cleave and release polypeptide

77
Q

In prokaryotes, transcription and translation are often _____. What enables this?

A

Coupled

Lack of nucleus in prokaryotes

Microbiology (24 decks)

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