3. Transcription and RNA Processing Flashcards Preview

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Flashcards in 3. Transcription and RNA Processing Deck (39):
1

Function rRNA

Most abundant type. Structural component of ribosome

2

Function tRNA

Second most abundant type. Carry amino acids to ribosome.

3

Function mRNA

Specifies amino acid sequence

4

Heterogenous nuclear RNA (hnRNA, pre-mRNA)

Only in nucleus, precursor of mRNA

5

Small nuclear RNA (snRNA)

Participates in splicing (removal of introns) of mRNA

6

Ribozymes have..

Enzymatic activity

7

Prokaryotic RNA polymerase (2)

- Synthesizes all types of RNA
- Core: alfa2,betabeta'.

8

Sigma factor

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

9

Rho factor

Sometimes needed to terminate transcription in prokaryotes

10

Rifampin

Inhibits prokaryotic RNA polymerase

11

Actinomycin D

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

12

Three eukaryotic RNA polymerases + function

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

13

Transcription factor IID

RNA polymerase II

14

Alfa-amanitin

- Toxin from certain mushrooms
- Inhibits RNA polymerase II

15

Binding site for RNA polymerases

Promotor region

16

First base transcribed as RNA

+1 base

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DNA coding strand is identical to..

mRNA

18

DNA template strand is..

Used for transcription

19

Bacterial/prokaryotic promotor contains two consensus sequences..

1. Pribnow box (TATA box)
2. -35 sequence

20

Rho-independent termination

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

21

Rho-dependent termination

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

22

In bacteria translation and transcription..

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

23

Prokaryotic ribosomes bind to..

Shine Dalgarno sequences in 5' UTR

24

Startcodon

AUG

25

Protein in synthesized from.. to..

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

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Monocistronic

One gene

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Polycistronic

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

28

Eukaryotic promotor contains two consensus sequences..

1. TATA box (-25, Hogness)
2. CAAT box (-70)

29

Posttranscriptional processing of mRNA in eukaryotes (2)

1. 7-methylguanosine cap to 5' end
2. Poly-A-tail to 3' end

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7-methylguanosine cap

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

31

Poly-A-tail

- 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

Splicing

Removes introns, lariat structure is degraded

33

Spliceosomes

Complexes of snRNA and protein (snRNP, snurp)

34

Example alternative splicing (2)

- Tropomyosin and troponin T
- Immunoglobulins (membrane-bound or secreted)

35

How can alternative splicing be detected?

By Northern Blot

36

Eukaryotic ribosomes

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

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Prokaryotic ribosomes

- 50S and 30S -> 70S ribosome
- 50S = 5S and 23S
- 30S = 16S

38

Shiga toxin and Verotoxin (ETEC)

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

39

RNA editing + give example

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