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(DIT) Rapid Fire + 4/5 Stars > RNA > Flashcards

RNA Flashcards

1
Q

RNA subtypes

A

mRNA: Largest
tRNA: transfers mRNA info to aa chain; smallest
rRNA: part of ribosome, binds aa together; most abundant

hnRNA: heterogeneous nuclear RNA

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2
Q

Sites of RNA synthesis

A

Nucleoplasm: mRNA, tRNA
Nucleolus: rRNA

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3
Q

Start codon

A

AUG – methionine

prokaryotes –formyl-methionine

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4
Q

Stop codons

A

UGA
UAA
UAG

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5
Q

Operon

A

Structural genes transcribed (coding region) + promoter region + all regulatory regions (enhancers and repressors)

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6
Q

Transcription factors

A

Bind to promoter region (-75 CCAAT box, -25 Hogness/TATA box, and -10 Pribnow/TATAAT box) in order for transcription to take place

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7
Q

Operator region

A

Binds repressor (stops transcription) or inducer (starts transcription), located between promoter and start site

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8
Q

Response elements

A

Enhancer region and repressor region
Increase or decrease rate of transcription when bound by protein factors
Location may be close to, far from, or within the promoter region

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9
Q

Common structural motifs

A

Helix-loop-helix
Helix-turn-helix
Zinc finger
Leucine zipper

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10
Q

Lac operon

A

Excess glucose and excess lactose: operon OFF, CAP not bound

  • lactose binds to lac repressor, changes shape and causes it to dissociate from DNA
  • if lactose absent, lac repressor is bound

Excess glucose, absent lactose: Operon OFF both – lac repressor bound and CAP not bound

Absent glucose causes CAP to bind

Absent glucose, absent lactose: Operon OFF, lac repressor bound

Absent glucose, excess lactose: Operon ON, RNA polymerase binds and RNA transcribed

CAP: catabolite activating protein – TF

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11
Q

Termination of prokaryotic RNA transcription

A

Rho factor of E coli – RNA-dependent ATPase) – energy of ATP knocks RNA poly off template

GC-rich DNA -> GC same strand binding forms stem-loop (hairpin) in RNA -> pause in RNA poly-> weak RNA bonds -> separation of RNA poly

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12
Q

RNA processing and splicing

A

Allows it to leave nucleus

Cap 5’ end: 7-methyl-guanosine by SAM (s-adenosyl-methionine)

Poly-A 3’ end – by poly-A polymerase (signal AAUAAA)

Remove interons – euk: splicosomes remove interons, spice together exons

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13
Q

Eukaryotic RNA polymerases

A

RNA poly 1: rRNA
RNA poly 2: mRNA
RNA poly 3: tRNA

(order of use)

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14
Q

Alpha-amantin

A

Mushroom toxin inhibits RNA poly II

Causes hepatotoxicity, liver failure

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15
Q

Prokaryotic RNA polymerase

A

Single RNA poly

Inhibited by rifampin

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16
Q

Rifamin – 4 Rs

A

Rifampin
RNA poly inhibitor
Red secretions
Revs up CYP450

17
Q

Protein translation

A

mRNA -> ribosome -> protein and rRNA

18
Q

Ribosomal subunits

A

Euk: 60S + 40S = 80S (Even)

PrOk: 50s (has 23 rRNA molecule) + 30s = 70S (Odd)

19
Q

Initiation of protein synthesis in prokaryote

A

Initiation factors IF-1, -2, -3

Assist in assembly of small ribosomal subunits (30S) to first tRNA – fMET

IF2 binds 30S then fMET tRNA binds at the P site (subsequent bind at the A site)

50S hydrolyses GTP on IF2 -> energy release
-50S attaches to 30S = 70S prok ribosome

20
Q

Linezolid action

A

Binds 50S, inhibits initiation of prok ribosome

21
Q

Tetracycline action

A

Late – prevents tRNA from binding A site

22
Q

Elongation

A

2nd step of protein synthesis

EF (elongation factors) required for subsequent tRNA to bind A site
Energy from GTP

50 S has peptidyl transferase activity – transfers aa from P site to aa on A site
-in 23 s rRNA in prok

Translocation – ribosome complex moves down mRNA 3 nt

  • > tRNA shift to next site: A-> P, P->E, E-> out to be recharged
  • requires EFG in prok and EF2 in euk

Stop codon : UGA, UAA, UAG terminates

23
Q

Chloramphenicol action

A

Inhibits 23S rRNA – blocking peptidyl transferase activity

24
Q

Antibiotics inhibiting 50S translocation step

A

Streptogramins
Lincomycin
Clindamycin
Macrolides

25
Q

Termination

A

3rd step of protein synthesis

don’t match tRNA
release factor binds to mRNA
-hydrolyses GTP
-releases polypeptide from ribosome
-subunits/complex disassociates
26
Q

Post translational modification possibilities

A

C- or N- terminal trimed

Covalent modifications: add molecule
-glycosylation, hydroxylation, phosphorylation

disulfide bonds

protein folding

  • primary structure aa sequence
  • secondary structure – alpha helix/beta pleated sheet
  • tertiary/quaternary structure- folding

(DIT) Rapid Fire + 4/5 Stars (162 decks)

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