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MB351 > Lecture 28/30 Microbial Genetics > Flashcards

Lecture 28/30 Microbial Genetics Flashcards

1
Q

What are the three ways that genetic information can be “used”?

A

expression, recombination, replication

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2
Q

Recombination

A

genetic information is transferred between cells of the same generation

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3
Q

Replication

A

genetic information is transferred between generations of cells

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4
Q

Expression

A

genetic information is used within the cell to produce the proteins for the cell to function

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5
Q

Where is DNA obtained from?

A

a parent cell or from another cell

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6
Q

Describe the genome of a prokaryote

A

singular, circular, DNA chromosome

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7
Q

Supercoiled

A

when a chromosome folds and compacts with the help of proteins to fit in the cell

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8
Q

General Dogma

A

replication –> transcription –> translation

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9
Q

Replication

A

DNA is copied

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10
Q

Transcription

A

DNA is converted to mRNA

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11
Q

Translation

A

mRNA directs protein synthesis

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12
Q

What organism can do reverse transcription?

A

viruses (ex. HIV)

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13
Q

What are the nucleotides that make up DNA?

A

adenine, thymine, cytosine, and guanine

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14
Q

What is the DNA backbone made of?

A

deoxyribose-phosphate

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15
Q

What are strands of DNA held together by?

A

hydrogen bonding
(C-G bond is stronger and thus harder to break)

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16
Q

Semiconservative Replication

A

One new strand and one old strand

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17
Q

Antiparallel

A

the backbone of one strand is upside down relative to the backbone of the other strand

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18
Q

Steps of DNA Replication

A

1) Gyrase- relieves supercoil
2) Helicase- unwinds double helix
3) binding proteins- stabilize unwound DNA
4) Primase- makes RNA primers for lagging strand
5) DNA polymerase
6) DNA ligase - joins discontinuous fragments

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19
Q

Direction of DNA Synthesis

A

5’-to-3’

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20
Q

Origin of replication

A

where replication is initiated

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21
Q

Replication fork

A

structure opened by DNA helicase

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22
Q

What shape is chromosome replication?

A

“theta-shaped”

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23
Q

Termination of Replication

A

where DNA synthesis is completed

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24
Q

DNA replication of bacterial DNA is ____.

A

bidirectional

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25
Q

What are the components of a protein encoding sequence (DNA)?

A

1) Promoter
2) RNA-coding sequence
3) Terminator

26
Q

What does the promoter do?

A

determines where to start transcription

27
Q

Operon

A

one DNA gene cluster transcribed as a single unit and controlled by the same elements; can contain multiple genes

28
Q

What part of DNA occurs right before the operon?

A

regulatory gene

29
Q

Components of the operon

A

1) Promoter
2) Operator
3) Structural genes

30
Q

Promoter

A

where RNA polymerase binds

31
Q

Polycistronic mRNA

A

an mRNA of a group of co-transcribed genes

32
Q

What is the purpose of polycistronic mRNA?

A

allows expression of related genes to be transcribed

33
Q

Why does transcription and translation happen simultaneously in bacteria?

A

no nuclear membrane, helps save the cell energy

34
Q

How is RNA different from DNA?

A

RNA is usually single stranded,
U instead of T,
ribose sugar

35
Q

What are the three types of RNA?

A

ribosomal RNA,
messenger RNA,
transfer RNA

36
Q

ribosomal RNA

A

helps ribosomes (catalytic role)

37
Q

transfer RNA

A

brings in amino acids during translation (functional role)

38
Q

messenger RNA

A

translated into protein (informational role)

39
Q

RNA Polymerase (RNAP)

A

transcribes DNA into RNA; reads DNA is the 3’-to-5’ direction; synthesis of RNA in the 5’-to-3’ direction

40
Q

Components of RNA Polymerase

A

1) Sigma factor- tells where to bind onto DNA (@ recognized promoter)
2) Core enzyme- synthesizes RNA, enzyme stability

41
Q

What does RNA polymerase do?

A
  • catalyzes the formation of phosphodiester bonds between ribonucleotides
  • requires DNA as a template
  • does NOT require primers
42
Q

Holoenzyme

A

core enzyme + sigma factor

43
Q

Components of the promoter

A

1) -35 sequence
2) -10 sequence
(these are highly conserved)

44
Q

What is +1?

A

the start site of transcription

45
Q

Rho-dependent

A

*Rho (terminator protein) is used to separate the template and polymerase

46
Q

Rho-independent

A

*inverted repeats cause hydrogen bonding that forms a stem-loop
*stem-loop causes the RNA polymerase to pause
*the mRNA will dissociate and the polymerase will release the DNA
*no enzymes needed

47
Q

Steps of transcription

A

1) Initiation: RNA polymerase binds to promoter; assisted by sigma factor that recognizes promoter
2) Elongation: RNA pol moves along and adds ribonucleotides to the 3’ end of the preceding ribonucleotide
3) Termination: transcription stops when it reaches the terminator sequence

48
Q

Components of mRNA

A

1) Leader
2) Reading Frame
3) Trailer

49
Q

Components of the reading frame

A

1) Start codon (AUG)
2) Codons (3 nucleotides)
3) Stop codon

50
Q

What does AUG code for in bacteria?

A

N-formylmethionine

51
Q

____ sense codons on mRNA encode for ____ amino acids.

A

64; 20

52
Q

Degenerate genetic code

A

different codons specify the same amino acid (usually last nucleotide is changed)

53
Q

What does tRNA do?

A

carries complementary anticodon

54
Q

Wobble position

A

base pairing is more flexible for 3rd base of codon than first two

55
Q

Components of ribosome

A

1) large subunit (50S)
- 23S rRNA –> forms peptide bonds
- 5S rRNA –> provides structural stability
2) small subunit (30S)
- 16S rRNA –> used in translation as a molecular guide

56
Q

Steps of Translation’s Initiation

There’s Three

A

1) 30S ribosomal subunit binds to Shine-Dalgarno box (AGGA), upstream of start codon (AUG)
2) Initiator aminoacyl-tRNA with formylmethionine (F-Met) binds to AUG (start codon)
3) 50s subunit binds onto this complex

57
Q

Sites of the 50s Ribosome

A

A site: acceptor site on the ribosome where new charged tRNA first attaches
P site: peptide site where the growing polypeptide is held by a tRNA
E site: exit site that the tRNA is released by the ribosome

58
Q

Steps of Translation’s Elongation

A

1) a new charged aminoacyl-tRNA enters the ribosome at the A site, binding to the codon
2) the 50S subunit catalyzes formation of a peptide bond between the 2 amino acids

59
Q

Steps of Translation’s Translocation

A

1) ribosome must advance 3 nucleotides down mRNA during translocation (requires protein EF-G)
2) after translocation, an empty tRNA sits in the E site and the peptidyl-tRNA is in the P site
3) tRNA in E site is ejected, a new aminoacyl-tRNA enters A site
4) process continues until a stop codon is reaches

60
Q

Steps of Translation’s Termination

A

1) stop codon/nonsense codon is reached
2) release factor proteins bind in the vacant A site
3) polypeptide released from tRNAs
4) ribosome falls apart (no tRNAs so it destabalizes)

MB351 (21 decks)

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