Translation

Question 1

Explain the Nirenberg and Matthaei experiments

Answer 1

Created codon table by using synthetic oligos (ex: poly-U for Phe) and then expanding

Question 2

2 classes of RNAs that contain large amounts of modified nucleosides

Answer 2

tRNA and rRNA

Question 3

What are the 6 required components of translation?

Answer 3

1. mRNA
2. aa-tRNAs
3. energy
4. ribosome
5. initiation, elongation, and release factors
6. recycling factors (RRFs)

Question 4

What charges tRNAs?

Answer 4

aa-tRNA synthetase

Question 5

What are the 2 domains of aa-tRNA synthetase?

Answer 5

1. catalytic domain that adds AA to tRNA
2. anticodon binding domain that insures the correct tRNA is charged

Question 6

What 2 factors make RNA decoding very specific?

Answer 6

1. charging tRNA with correct AA
2. codon-anticodon recognition

Question 7

What is a big factor of why wobble exists?

Answer 7

I can pair with A,U, or C

Question 8

How does anticodon use and tRNA genes relate?

Answer 8

more anticodon use = more tRNA gene copies

Question 9

50S subunit main 3 functions

Answer 9

1. catalytic site
2. peptidyl transferase
3. elongation

Question 10

30S subunit main 2 functions

Answer 10

1. binds mRNA site
2. selects aa-tRNA

Question 11

Shine-Delgarno sequence

Answer 11

Brings in the 30S ribosome to initiate translation

Question 12

IF1

Answer 12

Blocks A site

Question 13

IF2

Answer 13

initiates tRNA binding

Question 14

IF3

Answer 14

subunit dissociation

Question 15

EF-Tu

Answer 15

tRNA binding

Question 16

EF-G

Answer 16

translocation

Question 17

RF1 and RF2

Answer 17

termination

Question 18

RF3

Answer 18

release RF1 and RF2

Question 19

which initation factor binds to uncoupled 30S and causes release of tRNA and mRNA

Answer 19

IF3

Question 20

Which initiation factor blocks the binding of 50S

Answer 20

IF3

Question 21

which initation factor blocks the A site

Answer 21

IF1

Question 22

Which sequence is bound by the 16S RNA?

Answer 22

Shine-Delgarno

Question 23

which initiation factor positions the start codon at the P site

Answer 23

IF2

Question 24

which initiation factor guides fMet to the P site

Answer 24

IF2

Question 25

4 steps of completion of initiation

Answer 25

1. IF3 and IF1 are released
2. IF2-GTP facilitates 50S recuitment
3. GTP is hydrolyzed to GDP
4. IF2-GDP is leased

Question 26

7 Elongation steps

Answer 26

1. GTP bound EF-Tu binds to aa-tRNAs
2. EF-Tu/aa-tRNA complex translocates to A site
3. GTP to hydrolyzed to GDP
4. GDP bound EF-Tu leaves ribosome
5. A aa-tRNA bound to P aa-tRNA which ratches ribosome
6. EF-Ts releases GDP from EF-Tu so it can bind GTP again
7. EF-G binds the ratched form and pushes RNA over one codon

Question 27

RNAP alpha subunit CTD

Answer 27

directly couples transcription and translation (connects to ribosome)

Question 28

NusG

Answer 28

couples RNAP and ribosome

Question 29

termination steps

Answer 29

1. RF1/RF2 mimic tRNAs to break peptide chain
2. GDP to GTP RF3 releases RF1/RF2
3. RF3 released
4. RRF and EF-G bind and release 50S
5. IF1 and IF3 catalyze release of used tRNA and mRNA

Question 30

What is required to cleave the peptide chain in a ribosome?

Answer 30

GGQ motif in RF proteins

Question 31

Sec-insertion sequence (SECIS)

Answer 31

directs stop codon readthrough with selenocystine by stabilizing SelB and Sec

Question 32

SelB

Answer 32

places tRNA^sec