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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
What are the components of a protein encoding sequence (DNA)?
1) Promoter 2) RNA-coding sequence 3) Terminator
26
What does the promoter do?
determines where to start transcription
27
Operon
one DNA gene cluster transcribed as a single unit and controlled by the same elements; can contain multiple genes
28
What part of DNA occurs right before the operon?
regulatory gene
29
Components of the operon
1) Promoter 2) Operator 3) Structural genes
30
Promoter
where RNA polymerase binds
31
Polycistronic mRNA
an mRNA of a group of co-transcribed genes
32
What is the purpose of polycistronic mRNA?
allows expression of related genes to be transcribed
33
Why does transcription and translation happen simultaneously in bacteria?
no nuclear membrane, helps save the cell energy
34
How is RNA different from DNA?
RNA is usually single stranded, U instead of T, ribose sugar
35
What are the three types of RNA?
ribosomal RNA, messenger RNA, transfer RNA
36
ribosomal RNA
helps ribosomes (catalytic role)
37
transfer RNA
brings in amino acids during translation (functional role)
38
messenger RNA
translated into protein (informational role)
39
RNA Polymerase (RNAP)
transcribes DNA into RNA; reads DNA is the 3'-to-5' direction; synthesis of RNA in the 5'-to-3' direction
40
Components of RNA Polymerase
1) Sigma factor- tells where to bind onto DNA (@ recognized promoter) 2) Core enzyme- synthesizes RNA, enzyme stability
41
What does RNA polymerase do?
- catalyzes the formation of phosphodiester bonds between ribonucleotides - requires DNA as a template - does NOT require primers
42
Holoenzyme
core enzyme + sigma factor
43
Components of the promoter
1) -35 sequence 2) -10 sequence (these are highly conserved)
44
What is +1?
the start site of transcription
45
Rho-dependent
*Rho (terminator protein) is used to separate the template and polymerase
46
Rho-independent
*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
Steps of transcription
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
Components of mRNA
1) Leader 2) Reading Frame 3) Trailer
49
Components of the reading frame
1) Start codon (AUG) 2) Codons (3 nucleotides) 3) Stop codon
50
What does AUG code for in bacteria?
N-formylmethionine
51
____ sense codons on mRNA encode for ____ amino acids.
64; 20
52
Degenerate genetic code
different codons specify the same amino acid (usually last nucleotide is changed)
53
What does tRNA do?
carries complementary anticodon
54
Wobble position
base pairing is more flexible for 3rd base of codon than first two
55
Components of ribosome
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
Steps of Translation's Initiation | There's Three
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
Sites of the 50s Ribosome
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
Steps of Translation's Elongation
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
Steps of Translation's Translocation
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
Steps of Translation's Termination
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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