Test 2- Transcription And Translation Flashcards Preview

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Flashcards in Test 2- Transcription And Translation Deck (44):
1

Template strand

Read by RNA polymerase

2

Sense strand

Unread strand of DNA; look like RNA produced.

3

-35 box

TTGACA

4

Pribnow box

TATAAT

5

Prokaryotic holoenzyme

Core polymerase and sigma factor

6

Sigma factors

70- most promoters
32- heat shock
54- nitrogen starvation
28- motility and chemotaxis

7

Prokaryotic transcription initiation and elongation

RNA polymerase binds
~10nt added
Sigma factor released
Elongation
3' and 5' exonuclease and endonuclease activity

8

Exonuclease

1 bp at a time

9

Endonuclease

Multiple bps at a time

10

Prokaryotic transcription termination

Terminator sequences signal end
-rho dependent vs. rho independent

11

Rho independent

Inverted repeat ~20 bp upstream of termination followed by 4-8 AT bps
Forms hairpin loop
RNA pol terminates bc of weak AU bps

12

Rho dependent

Rho protein binds to terminator sequence and uses ATPase to dissociate RNA pol

13

Prokaryotic v. Eukaryotic transcription

mRNA processing
RNA polymerase

14

Euk. RNA pol

Pol I- 28s, 18s, 5.8s rRNA
Pol II- mRNA, snRNA
Pol III- tRNA, 5s RNA, snRNA

15

Euk. Promoter

Core promoter: TATAAAA ~-30
Proximal promoter: CAAT ~-75
+enhancers binding to gene reg. proteins

16

Euk. Transcription initiation

TFIID (TBP + TAFs) binds to TATA box
TFIIA and TFIIB bind
RNA pol II w/ TFIIF binds
TFIIE and TFIIH bind to form complete txn initiation complex

17

5' cap

7-methyl guanosine
Cotranscriptional
After synthesis of ~20nt
Protects from exonucleases
Required for exiting nucleus
Binds 5'-5'
Methylates 1-3 sugars

18

Polyadenylation

50-200 As
Required for nuclear export
Cotranscriptional
CPSF, CstF, and CFI and CFII bind and cleave at polyA site
PAP and PABII add As

19

Splicing

5'GU and 3' AG recognized
snRNPs (snRNA + protein) form spliceosome with mRNA
SnRNA- U12456
U1- binds 5' junction
U2- binds branch point
U4u6u5 bind and form loop
U4 dissociates
5' junction cleaved intron attaches to branch point A
3' cleavage
Exons ligate

20

Prok. rRNA txn

Multiple RNA encoded in one unit of DNA which is separated by spacers

21

RNA pol I

Non transcribed, external, and internal transcribed spacers separate 18, 5.8, and 28s rRNA

22

RNA pol III

5s rRNA, tRNA, snRNA
Promoters for rRNA and tRNA within coding region.

23

RNA editing

Editing of mitochondrial mRNA postranscriptionally

24

Primary structure

Amino acid sequence

25

Secondary structure

a-helix and b-sheets formed by hydrogen bonding

26

Tertiary structure

Further polypeptide folding

27

Quaternary structure

Multiple polypeptide units bound

28

Triplet code discovery

Experiments by crick and brenner with t4
Base deletions, additions caused frame shifts

29

Characteristics of genetic code

Triplet
Continuous
Non overlapping
Nearly universal
Degenerate
Start and stop signals
Wobble

30

Start codon

Aug

31

Stop codons

UAG
UAA
UGA

32

Wobble codes

G an U can pair
I can pair with AUC

33

tRNA

From spacer regions of rRNA
Anticodon in loop II
Amino acid attached to CCA3'

34

Aminoacylation

aa-tRNA synthetase binds amino acid and ATP
ATP is hydrolyzed
uncharged tRNA binds to enzyme
aa transferred to tRNA

35

Prokaryotic ribosome

70s ribosome
50 S large subunit
23S and 5s rRNA
30S small subunit
16 S rRNA

36

Eukaryotic ribosome

80s ribosome
60s large subunit
28s, 5.8s, 5s rRNA
40s small subunit
18s rRNA

37

Prokaryotic translation initiation

Shine Dalgarno sequence recognized by small subunit with IF 1&3
fMet binds with help of IF2
Large subunit is recruited
GTP hydrolyzed; IFs leave

38

Eukaryotic translation initiation

eIF-4F binds to mRNA 5'cap
40s, eIFs, GTP, met-tRNA bind
Complex scans mRNA for AUG in Kozak consensus sequence
60s binds; eIFs leave

39

Translation elongation

fMet-tRNA is in p site
Next aa-tRNA binds at A site with EF-tu and GTP
Peptidyl transferase catalyzes joining of aas
Ribosome translocates using EF-G and GTP
Uncharged tRNA is released through E site

40

Polysome

Multiple ribosomes translating one mRNA

41

Translation termination

RF1 binds to stop codon
Polypeptide chain released
RF3-GDP binds releasing RF1
GTP is hydrolyzed to release RF3
RRF binds to A site
EF-G-GTP binds and hydrolyzes GTP to translocate ribosome
EF-G releases RRF releases tRNA
Ribosome dissociates

42

Release factors

E. coli
RF1 for UAA and UAG
RF2 for UAA and UGA
RF3 stimulates termination
Eukaryotes
eRF1 recognizes all codons
eRF3 stimulates termination

43

Secreted proteins

Signal peptide is bound by SRP stopping translation
SRP binds to docking protein
Signal peptide binds to signal peptidase
translation resumes and peptide goes into ER lumen
Signal peptide cleaved
Translation completes polypeptide released into ER

44

SRP

Signal recognition particle
Polypeptide+RNA
RNA Blocks A site
Polypeptide recognizes signal peptide and docking protein