Dr Hack's Lectures

Question 1

Genetic information is copied to RNA via

Answer 1

Transcription

Question 2

RNA provides information to make specific amino acid sequences by

Answer 2

Translation

Question 3

What is the charge on phosphate?

Answer 3

Negative

Question 4

What joins amino acids to the corresponding tRNA

Answer 4

Aminoacyl-tRNA synthetase

Question 5

What is the start codon?

Answer 5

AUG

Question 6

What are the stop codons?

Answer 6

UAG, UGA, UAA

Question 7

Anticodon in tRNA binds to

Answer 7

codon in mRNA

Question 8

Where does protein synthesis take place?

Answer 8

Ribosomes

Question 9

In the initiation mechanism, what binds to P site? (bacteria/eukaryotes)

Answer 9

Methionyl-tRNA (eukaryotes)

Formethyionyl-tRNA (bacteria)

Question 10

Where does the aminoacyl-tRNA for the second amino acid bind?

Answer 10

A site

Question 11

Name the steps of protein synthesis

Answer 11

mRNA bound to small subunit
Ribosome transfers amino acid from peptidyl-tRNA in P site to new aminoacyl-tRNA in A site
Large subunit moves relative to smell subunit
Ribosome reset

Question 12

Where is tRNA ejected form?

Answer 12

E site

Question 13

Where does energy for protein synthesis come from?

Answer 13

Hydrolysis of GTP

Question 14

What does EF-Tu do?

Answer 14

Carries aminoacyl-tRNA to ribosome and binds to GTP, hydrolyses GTP to GDP and phosphate is base pairing correct

Question 15

What does EF-G do?

Answer 15

Hydrolyses GTP and helps reset ribosome for next amino acid to pair

Question 16

How is translation terminated?

Answer 16

Release factor protein binds to A site instead of tRNA
Peptidyl tRNA bond hydrolysed
Protein released

Question 17

What is an operon

Answer 17

A cluster of genes in bacteria

Question 18

What does AUG code for

Answer 18

Methionine

Question 19

Where does transcription start in bacteria?

Answer 19

3’ of rRNA binds to a Shine-Dalgarno sequence

Question 20

Transcription moves which direction?

Answer 20

5’ N terminus –> 3’ C terminus

Question 21

What two regions conserve most promoters?

Answer 21

-35, -10

Question 22

What can a core enzyme not recognise? What does it need to do this?

Answer 22

Specific promoter sequence, needs a sigma factor and forms a holoenzyme

Question 23

Transcription is catalysed by ______?

Answer 23

RNA Polymerase

Question 24

Translation occurs on ________?

Answer 24

Ribosomes

Question 25

Transcription in bacteria depends on ______?

Answer 25

interaction between sigma factor and promoter

Question 26

What two sugars make up Lactose?

Answer 26

Glucose and Galactose

Question 27

Role of lactose permease?

Answer 27

Transports lactose into cell

Question 28

Role of beta galactosidase?

Answer 28

Hydrolyses Lactose into glucose and galactose

Question 29

What are the 3 genes transcribed together in the lac operon?

Answer 29

lacZ, lacY, lacA

Question 30

How does E. coli use glucose?

Answer 30

Preferentially

Question 31

When is the lac operon transcribed?

Answer 31

Lactose PRESENT and glucose ABSENT

Question 32

Who studied the lac operon and received the Nobel prize in 1965?

Answer 32

Jacob, Lwoff and Monod

Question 33

What is a simple way to detect mutants in the lac operon?

Answer 33

Screen for beta-galactosidase activity

Question 34

What does an activator molecule in the lac operon do?

Answer 34

Increase transcription when lactose is present

Question 35

What does a repressor molecule in the lac operon do?

Answer 35

decrease transcription when lactose is absent

Question 36

When would the lac operon be transcribed when glucose is absent in a cell with a non-functional operator?

Answer 36

Never (non-inducible)

Question 37

When would the lac operon be transcribed when glucose is absent if the signal molecule cannot bind to the repressor?

Answer 37

All the time (constitutive)

Question 38

When Oc mutants are bound, is the operon transcribed?

Answer 38

Yes

Question 39

When the i^s mutant is present, is the lac operon transcribed?

Answer 39

No, the repressor cannot dissociate from the operator, lac operon not transcribed

Question 40

What is the natural signal molecule called?

Answer 40

Allolactose

Question 41

What does allolactose do when lactose is present?

Answer 41

Binds to the repressor, causing it to dissociate from the operator, lac operon is transcribed

Question 42

What is allolactose's role when lactose is present?

Answer 42

Binds to repressor causing it to dissociate from the operator, allows transcription

Question 43

How are we able to identify where a protein binds to DNA?

Answer 43

in vitro DNase protection experiments - sequencing protected DNA shows where the protein binds

Question 44

How does the repressor and the operator interact with each other?

Answer 44

Binding sites overlap

Question 45

What are the 4 regions of the lac repressor structure?

Answer 45

N-terminal DNA binding domain Hinge region Allolactose binding central domain C-terminal domain

Question 46

What are the 3 auxiliary operators?

Answer 46

o1, o2, o3

Question 47

Where is o2 in relation to lacZ gene?

Answer 47

410bp downstream

Question 48

What is a cis acting mutation?

Answer 48

affects expression of gene/operon in SAME DNA molecule

Question 49

what is a trans acting mutation?

Answer 49

affects expression of gene/operon in DIFFERENT DNA molecule