DNA, RNA...Replication, Transcription, Translation

Question 1

1) Initiator protein that binds replicator in E.coli?
2) DNA helicase?
3) Single-stranded binding protein?
4) Topoisomerase?
5) DNA Pol 1

Answer 1

1) DNA A
2) Untwists helix
3) Prevents re-annealing
4) Relaxes strand behind the fork
5) Remove RNA primer and add DNA

Question 2

In eukaryotes:

1) Pol alpha
2) Pol delta
3) Pol epsilon

Answer 2

1) Initiates new strands by primase
2) Lagging strand synthesis
3) Leading strand synthesis

Question 3

Telomerase?

Answer 3

Synthesizes telomere DNA using RNA template(reverse transcriptase)

Question 4

RNA can have unconventional base pairs…give an example

Answer 4

G-U or G-A
(these are mainly in rRNA)

Question 5

1) RNA has what at the 2’ end?
2) What does it do?

Answer 5

1) OH
2) Prevents it from forming a B-form helix(it resembles the A-form)

Question 6

T/F: Bacterial mRNA is monocistronic(codes for 1 protein only)

Answer 6

False. Bacterial mRNA is polycistronic…Eukaryotic mRNA is monocistronic

Question 7

1) How many loops are in tRNA?
2) Which binds the codon

Answer 7

1) 4
2) II

Question 8

1) Most abundant form of RNA in a cell?
2) Regions of DNA that contain genes for that RNA are called?
3) Mature form of that RNA consists of?

Answer 8

1) rRNA
2) rDNA/rRNA transcription units
3) 5.8s, 18s, 28s

Question 9

1) Sigma factor?
2) 2 examples

Answer 9

1) Makes sure holoenzyme binds in a stable way to promoter
2) sigma 70 and sigma 32(heat, stress)

Question 10

Rho-independent(type 1) vs Rho-dependent(type 2) termination?

Answer 10

RNA pol terminates transcription vs Rho helicase terminating transcription

Question 11

Eukaryotic RNA Pol’s?

Answer 11

Pol 1: rRNA
Pol 2: mRNA, snRNA
Pol 3: tRNA, 5s rRNA, snRNA

Question 12

RNA pol subunits?

Answer 12

Core: RBP 1,2,3,11
Common: RBP 5,6,8,10,12 (in all 3)
Non-essential: RBP 4,9

Question 13

In which class of promoters is spacing crucial for transcription control?

Answer 13

Class I

Question 14

1) 5’ cap enzyme?
2) 3’ Poly(A) tail enzyme?

Answer 14

1) guanylyltransferase(m7G)
2) Poly A polymerase

Question 15

Termination of transcription in eukaryotes involves?

Answer 15

XRN 2 exonuclease

Question 16

snRNP’s order of binding?

Answer 16

U1 - U2 - U4/U6 + U5 - U4 dissociates(active spliceosome)

Question 17

mRNP exporter steps?

Answer 17

• REF recruits NXF 1, NXT1
• CBC to 5’, PABPN1 to poly (A)

Question 18

Translation in bacteria?

Answer 18

Initiation:
- 30s has IF 1(blocks A site) and IF 3(prevents binding of 50s)
- Binds to mRNA via AUG and Shine dalgarno
- f-met tRNA + IF 2(carries GTP) binds to complex at P site
= 30s initiation complex
- 50s binds and IF’s released

Elongation:
- Aminoacyl tRNA to A site + EF
- Peptidyl transferase
- EF-G + GTP hydrolysis = translocation

Termination:
- Release factors(RF) recognize stop codons
- RF 1, UAA, UAG
- RF 2, UAA, UGA
- RF 3-GDP releases RF 1,2 and GTP hydrolysis releases RF 3
- RRF binds to A site, translocates to P, releases uncharged tRNA at E
- EF-G releases RRF and disassemble

Question 19

Translation in Eukaryotes?

Answer 19

Initiation:
- 40s + eIF4F(cap-binding protein eIF4E) + Met tRNA scan for AUG(in Kozak sequence) and bind
- 60s binds and eIF’s displaced except eIF4F
- 80s initiation complex
- PABP II binds to eIF4G = poly (A) stimulates initiation

Elongation:
- Same as bacteria

Termination:
- eRF 1 recognizes all stop codons
- eRF 3 terminates