Miles - Gene Regulation II/III

Question 1

Missense Mutation

Answer 1

Substitution codes for different amino acid

Question 2

Nonsense mutation

Answer 2

Substitution codes for stop codon

Question 3

Silent Mutation

Answer 3

Results in code for same AA

Question 4

Frame Shift

Answer 4

Worst if not addition/deletion by multiple of 3 Interrupts the entire reading frame

Question 5

Wobble Pairing

Answer 5

3rd base pair not strict, some overlap–conserves resources Allow G-U, Inosine - U, C, or A

Question 6

How does tRNA attach AAs?

Answer 6

tRNA requires ATP to be charged with proper AAs by aminoacyl tRNA synthase

Question 7

Bacterial Initiation

Answer 7

IF-1, IF-2 bind 30S (small) ribosomal subunit.

N-formylmethionyl tRNA joins

IF-2 bound to GTP

50S subunit binds

70S complex formed

NO Poly A Tail

Question 8

Eukaryotic Initiation

Answer 8

Small ribosomal subunit + initiation tRNA bind initiation codon

Complex associates with large ribosomal subunit

= functional

Question 9

What is eukaryotic initiation aided by?

Answer 9

Initiation Factors

Question 10

43S Preinitiation Complex:

Answer 10

IF1, IF1A, IF3 bind 40S

Initiator methionyl-tRNA, IF2 bound to GTP, and IF5 bind to ribosome complex

Question 11

How is mRNA prepared during eukaryotic initiation?

PABP

IF4F

IF4E

IF4G

IF4B

Answer 11

PABP bind 3’ poly-A tail

IF4F complex bind mRNA

IF4E binds methylguanine 5’ cap

IF4G keeps it all together

IF4B unwinds mRNA

Question 12

What does the ribosomal scanning of mRNA to find AUG start codon require?

What aids it?

Answer 12

ATP

Kozac sequence

Question 13

What triggers GTP hydrolysis once start codon is found?

Answer 13

IF5 triggers GTP hydrolysis by IF2

Question 14

How is eukaryotic initiation regulated?

Answer 14

GTP dependent steps

Two MET codes:

1. Initiator (AUG)

Internal sequence MET

Question 15

What organelle catalyzes peptide bond formation in growing polypeptide chains?

Answer 15

Ribosome

Question 16

What are the three tRNA binding sites in the ribosome, and what does each do?

Answer 16

A (acceptor) - Holds incoming tRNA

P (peptidyl) - Carries growing peptide chain

E (exit) - Empty tRNA exits

Question 17

What brings charged tRNA to the ribosome?

Answer 17

EF1alpha (elongation factor)

Question 18

What induces hydrolysis of ER1alpha/GTP?

Answer 18

Conformational change of ribosome

Question 19

What enzyme catalyzes the peptide bond formation occuring in the ribosome?

Answer 19

Peptidyltransferas3

Question 20

What two toxins can inhibit the elongation process?

Answer 20

Diptheria Toxin - inactivates EF-2

Ricin - cleaves adenine residue from 60S subunit and EF-2 can’t bind

Question 21

How is elongation regulated?

Answer 21

EF-1alpha must be recharged, promoted by EF1BravoGamma

Question 22

What signals termination? Specific codons:

Answer 22

UAA

UAG

UGA

Question 23

What aids the breaking of the ribosomal units during termination?

Answer 23

Release Factors (RFs)

Question 24

What recognizes the stop codon, and what occurs next?

Answer 24

RF-1 recognizes codon, binds RF-3/GTP, and enters the A-site.

Dissociation follows

Question 25

How is protein sythesis regulated by repressors?

Answer 25

Repressor can bind 3’ or 5’ UTR

Question 26

What are the regulatory regions for iron movement?

What occurs when Iron is absent?

Answer 26

Iron Regulatory Protein (IRP) can bind to Iron Response Element (IRE)

IRP can bind to the IRE at the 5’ UTR

Question 27

What are two ways Initiation Factors are regulated?

Answer 27

Phosphorylation/Dephosphorylation

Energy Dependent steps (ATP/GTP)

Question 28

What must happen to IF-4E to bind the cap and form the complex?

Answer 28

Phosphorylation

Question 29

Streptomycin

Answer 29

Inhibits initiation by binding to and distorring 30S

Question 30

Tetracyclines

Answer 30

Blocks access to A-site

Question 31

Chloraamphenicol

Answer 31

Inhibits peptidytransferase of 50S ribosome

Question 32

Erythromycin, Clindamycin

Answer 32

Inhibit translocation of ribosome by binding 50S subunit

Question 33

Puromycin (how is it unique?)

Answer 33

Causes premature release from A-site

Prokaryotic AND Eukaryotics