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Micro > L11: Genome Replication and Expression > Flashcards

L11: Genome Replication and Expression Flashcards

1
Q

Overview of DNA replication

A

bidirectional
semi-conservative
strands separate
each strand is a template for the synthesis of a new strand

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2
Q

What’s different about DNA replication in eukaryotes and prokaryotes?

A

Eukaryote- multiple oris

Prokaryote- single ori

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3
Q

How is the origin of replication selected in prokaryotes?

A

Protein DnaA binds and “opens” ori

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4
Q

What enzyme catalyzes DNA synthesis in 5’ to 3’ direction?

A

DNA polymerase

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5
Q

What does DNA polymerase need for DNA synthesis?

A

template
deoxynucleotide triphosphates
primer (usually RNA with 3’ OH group)

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6
Q

What enzyme breaks H bonds between DNA strands?

A

helicase

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7
Q

What enzyme underwinds DNA and relieves supercoiling?

A

Gyrase (topoisomerase)

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8
Q

What enzyme lays down RNA primers?

A

DNA primase

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9
Q

What enzyme removes RNA primers and fills in the gaps?

A

DNA pol I

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10
Q

What enzyme is a target for ciprofloxacin antibiotic?

A

Gyrase

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11
Q

How are genetic instructions stored and organized in DNA?

A

DNA sequence of a gene corresponds to amino acid sequence of protein encoded

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12
Q

What enzyme is used for transcription in bacteria?

A

RNA polymerase

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13
Q

What is the target of rifampin (antibiotic)

A

RNA polymerase

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14
Q

What are sigma factors?

A

proteins that direct core of RNA polymerase to promoters

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15
Q

What is sigma^s important for?

A

stationary phase

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16
Q

What are the 3 types of RNA generated by transcription in bacteria?

A

tRNA
rRNA
mRNA

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17
Q

What is tRNA used for?

A

carries amino acids during protein synthesis

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18
Q

What is rRNA used for?

A

component of ribosomes

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19
Q

What is mRNA used for?

A

template for protein synthesis

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20
Q

What are the key features of the structure of RNA (that make it different from DNA)

A

ribose instead of deoxyribose
uracil replaces thymine
usually single-stranded

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21
Q

What is the terminator in transcription?

A

sequence that signals RNA pol to stop

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22
Q

What enzyme opens and unwinds DNA without the need for a primer?

A

RNA polymerase

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23
Q

When does the sigma factor leave?

A

after transcription is initiated

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24
Q

What are the two types of terminators?

A

Rho-independent transcription termination

Rho-dependent transcription termination

25
Q

What type of nucleic acid is a terminator?

A

DNA

26
Q

Which type of terminator causes RNA pol to release?

A

Rho-independent

27
Q

What type of terminator causes RNA pol to pause (initially)

A

Rho-dependent

28
Q

What does the protein Rho do to stop transcription?

A

binds to RNA, then moves toward RNA pol and causes release

29
Q

How do bacteria control gene transcription in response to their environment?

A

two-component signal transduction systems

30
Q

Where does transcription in prokaryotes occur?

A

cytoplasm

31
Q

Where does transcription in eukaryotes occur?

A

nucleus

32
Q

What do eukarya need for transcription?

A 
RNA polymerase
Transcription factors (no sigmas)
33
Q

What is the promoter element for transcription in Eukarya?

A

TATA box

34
Q

What process removes introns?

A

RNA splicing

35
Q

What modifications need to be made to mRNA in Eukarya?

A

capping - methylguanosine added at 5’ end

Polyadenylation - adenine nucleotides added at 3’ end - tail

36
Q

What is translation?

A

synthesis of polypeptides directed by mRNA sequence

37
Q

What does translation require?

A

ribosomes

energy in the form of ATP and GTP

38
Q

What are the 2 subunits of bacterial ribosomes?

A

30S and 50S

39
Q

What type of rRNA acts as a ribozyme

A

23S rRNA

40
Q

What type of rRNA is capable of peptidyltransferase

A

23S rRNA

41
Q

What type of rRNA aligns mRNA with the ribosome?

A

16S rRNA

42
Q

What type of rRNA has a sequence complementary to Shine-Dalgarno sequence of the mRNA

A

16S rRNA

43
Q

What do ribosomes do?

A

“read” mRNA as a code

44
Q

code is ____ - multiple codons can encode the same amino acid

A

degenerate

45
Q

codons are read as a ____ made up of __ nucleotides

A

triplet, 3 nucleotides

46
Q

How many codons are there?

A

64

47
Q

How many nonsense codons are there?

A

3 (stop codons)

48
Q

How many sense codons are there?

A

61 (specify amino acids)

49
Q

What enzyme attaches an amino acid to the 3’ end of the correct tRNA molecule?

A

Synthetase

50
Q

What is the shape of tRNAs?

A

clover

51
Q

What is the anticodon?

A

complementary to codon in mRNA

52
Q

What are the 3 stages of translation?

A

initiation
elongation
termination

53
Q

What are the 3 sites on the ribosome?

A

A
P
E

54
Q

What occurs during initiation of translation?

A

AUG codon binds to P site, tRNA attaches Met amino acid

55
Q

What occurs during elongation of translation?

A

Next tRNA binds to A site, peptide bond forms between P and A site amino acids, everything shifts down and process continues

56
Q

What occurs during elongation of translation?

A

Next tRNA binds to A site, peptide bond forms between P and A site amino acids, everything shifts down and process continues

57
Q

What occurs during termination of translation?

A

Any one of the 3 stop codons enters, no tRNAs carry anticodon
release factors cleave and release the polypeptide

58
Q

What binds to single-stranded DNA after strands are separated to keep them separated?

A

SSB proteins (single-stranded binding proteins)

59
Q

What enzyme has 3’ -> 5’ proofreading activity?

A

DNA pol III

Micro (15 decks)

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