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Molecular Biology 1 > Dr Hack's Lectures > Flashcards

Dr Hack's Lectures Flashcards

1
Q

Genetic information is copied to RNA via

A

Transcription

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2
Q

RNA provides information to make specific amino acid sequences by

A

Translation

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3
Q

What is the charge on phosphate?

A

Negative

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4
Q

What joins amino acids to the corresponding tRNA

A

Aminoacyl-tRNA synthetase

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5
Q

What is the start codon?

A

AUG

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6
Q

What are the stop codons?

A

UAG, UGA, UAA

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7
Q

Anticodon in tRNA binds to

A

codon in mRNA

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8
Q

Where does protein synthesis take place?

A

Ribosomes

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9
Q

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

A

Methionyl-tRNA (eukaryotes)

Formethyionyl-tRNA (bacteria)

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10
Q

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

A

A site

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11
Q

Name the steps of protein synthesis

A

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

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12
Q

Where is tRNA ejected form?

A

E site

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13
Q

Where does energy for protein synthesis come from?

A

Hydrolysis of GTP

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14
Q

What does EF-Tu do?

A

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

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15
Q

What does EF-G do?

A

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

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16
Q

How is translation terminated?

A

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

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17
Q

What is an operon

A

A cluster of genes in bacteria

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18
Q

What does AUG code for

A

Methionine

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19
Q

Where does transcription start in bacteria?

A

3’ of rRNA binds to a Shine-Dalgarno sequence

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20
Q

Transcription moves which direction?

A

5’ N terminus –> 3’ C terminus

21
Q

What two regions conserve most promoters?

22
Q

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

A

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

23
Q

Transcription is catalysed by ______?

A

RNA Polymerase

24
Q

Translation occurs on ________?

25
Q

Transcription in bacteria depends on ______?

A

interaction between sigma factor and promoter

26
Q

What two sugars make up Lactose?

A

Glucose and Galactose

27
Q

Role of lactose permease?

A

Transports lactose into cell

28
Q

Role of beta galactosidase?

A

Hydrolyses Lactose into glucose and galactose

29
Q

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

A

lacZ, lacY, lacA

30
Q

How does E. coli use glucose?

A

Preferentially

31
Q

When is the lac operon transcribed?

A

Lactose PRESENT and glucose ABSENT

32
Q

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

A

Jacob, Lwoff and Monod

33
Q

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

A

Screen for beta-galactosidase activity

34
Q

What does an activator molecule in the lac operon do?

A

Increase transcription when lactose is present

35
Q

What does a repressor molecule in the lac operon do?

A

decrease transcription when lactose is absent

36
Q

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

A

Never (non-inducible)

37
Q

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

A

All the time (constitutive)

38
Q

When Oc mutants are bound, is the operon transcribed?

39
Q

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

A

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

40
Q

What is the natural signal molecule called?

A

Allolactose

41
Q

What does allolactose do when lactose is present?

A

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

42
Q

What is allolactose’s role when lactose is present?

A

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

43
Q

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

A

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

44
Q

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

A

Binding sites overlap

45
Q

What are the 4 regions of the lac repressor structure?

A

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

46
Q

What are the 3 auxiliary operators?

A

o1, o2, o3

47
Q

Where is o2 in relation to lacZ gene?

A

410bp downstream

48
Q

What is a cis acting mutation?

A

affects expression of gene/operon in SAME DNA molecule

49
Q

what is a trans acting mutation?

A

affects expression of gene/operon in DIFFERENT DNA molecule

Molecular Biology 1 (3 decks)

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