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Biochemistry > 3. Transcription and RNA Processing > Flashcards

3. Transcription and RNA Processing Flashcards

1
Q

Function rRNA

A

Most abundant type. Structural component of ribosome

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2
Q

Function tRNA

A

Second most abundant type. Carry amino acids to ribosome.

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3
Q

Function mRNA

A

Specifies amino acid sequence

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4
Q

Heterogenous nuclear RNA (hnRNA, pre-mRNA)

A

Only in nucleus, precursor of mRNA

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5
Q

Small nuclear RNA (snRNA)

A

Participates in splicing (removal of introns) of mRNA

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6
Q

Ribozymes have..

A

Enzymatic activity

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7
Q

Prokaryotic RNA polymerase (2)

A
  • Synthesizes all types of RNA

- Core: alfa2,betabeta’.

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8
Q

Sigma factor

A

Required for initiation of transcription in prokaryotes (helps RNA polymerase to recognize promotor region), released immediately after initiation

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9
Q

Rho factor

A

Sometimes needed to terminate transcription in prokaryotes

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10
Q

Rifampin

A

Inhibits prokaryotic RNA polymerase

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11
Q

Actinomycin D

A

Binds to DNA, prevents transcription (pro- and eukaryotes)

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12
Q

Three eukaryotic RNA polymerases + function

A
  • RNAP I: nucleolus, 28S, 18S and 5.8S rRNAs
  • RNAP II: nucleoplasm, hnRNA/mRNA, some snRNA
  • RNAP III: nucleoplasm, tRNA, soms snRNA, 5S rRNA
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13
Q

Transcription factor IID

A

RNA polymerase II

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14
Q

Alfa-amanitin

A
  • Toxin from certain mushrooms

- Inhibits RNA polymerase II

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15
Q

Binding site for RNA polymerases

A

Promotor region

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16
Q

First base transcribed as RNA

A

+1 base

17
Q

DNA coding strand is identical to..

A

mRNA

18
Q

DNA template strand is..

A

Used for transcription

19
Q

Bacterial/prokaryotic promotor contains two consensus sequences..

A
  1. Pribnow box (TATA box)

2. -35 sequence

20
Q

Rho-independent termination

A

GC-rich hairpin (=stem + loop) + 6-8 U residues (in newly formed RNA)

21
Q

Rho-dependent termination

A

Rho binds to newly formed RNA and displaces RNA polymerase from 3’ end of RNA. Also stem and loop (G-C rich hairpin)

22
Q

In bacteria translation and transcription..

A

Can occur simultaneously (no processing of mRNA, no introns)

23
Q

Prokaryotic ribosomes bind to..

A

Shine Dalgarno sequences in 5’ UTR

24
Q

Startcodon

A

AUG

25
Q

Protein in synthesized from.. to..

A

Amino terminus (5’) to carboxyl terminus (3’)

26
Q

Monocistronic

A

One gene

27
Q

Polycistronic

A

Related genes groups together are transcribed as one unit (eg lactose operon)
Only in bacteria

28
Q

Eukaryotic promotor contains two consensus sequences..

A
  1. TATA box (-25, Hogness)

2. CAAT box (-70)

29
Q

Posttranscriptional processing of mRNA in eukaryotes (2)

A
  1. 7-methylguanosine cap to 5’ end

2. Poly-A-tail to 3’ end

30
Q

7-methylguanosine cap

A

While still being synthesized: ribosome binding site + protection from degradation

31
Q

Poly-A-tail

A
  • Poly-A addition signal is AAUAAA, cut by endonuclease
  • Poly-A-polymerase adds poly-A tail (200 As)
  • Protects from degradation and aids in transport
32
Q

Splicing

A

Removes introns, lariat structure is degraded

33
Q

Spliceosomes

A

Complexes of snRNA and protein (snRNP, snurp)

34
Q

Example alternative splicing (2)

A
  • Tropomyosin and troponin T

- Immunoglobulins (membrane-bound or secreted)

35
Q

How can alternative splicing be detected?

A

By Northern Blot

36
Q

Eukaryotic ribosomes

A
  • 40S and 60S -> 80S ribosome
  • RNAPI (45S -> 28S, 18S, 5.8S)
  • RNAPIII (5S)
37
Q

Prokaryotic ribosomes

A
  • 50S and 30S -> 70S ribosome
  • 50S = 5S and 23S
  • 30S = 16S
38
Q

Shiga toxin and Verotoxin (ETEC)

A

Inactivate 28S rRNA in 60S subunit. RNA glycosylases remove single adenine residue from 28S, prevents aminoacyl-tRNA binding to ribosome.

39
Q

RNA editing + give example

A

Insertion, deletion, base alterations

- Cytosine to uracil deamination of apoprotein B gene (B100 in liver, B48 in intestines due to stop codon)

Biochemistry (18 decks)

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