Week 3

Question 1

Promoter

Answer 1

where RNA polymerase is recruited

Question 2

Regulatory proteins (2 points)

Answer 2

• Often upstream and near operon

- Bind to operon

Question 3

Protein properties (2 points)

Answer 3

• Physical (primary, secondary, tertiary structure; mass)

- Chemical (charge, activity, hydrophobicity)

Question 4

LacZ

Answer 4

Cleaves lactose into glucose and galactose only when glucose runs out

Question 5

LacI in absence of lactose (2 steps, 1 point)

Answer 5

• Binds to DNA at operator sequence
• inhibits transcription of Lac operon
• Always at equilibrium

Question 6

cAMP (2 points)

Answer 6

• Low at high glucose. High at low glucose.

- Binds CAP proteins, inducing transcription of catabolic operons

Question 7

trpR repressor

Answer 7

binds to trp Operon’s sequence only when trp is present. (regulates anabolic process!)

Question 8

Leader sequence at high trp concentration (3 steps)

Answer 8

• Ribosome proceed through leader sequence fast
• Stem-loop structure
• Kick off RNA polymerase
• Repression of subsequent transcription

Question 9

Quorum sensing

Answer 9

Concentration of cell’s own population activates gene transcription and translation.

Question 10

Allosteric inhibition

Answer 10

Binds not to active site. Only changes activity

Question 11

Metabolic control inhibition

Answer 11

1 species slows down process

Question 12

Desensitisation

Answer 12

feedback circuit shuts off receptor

Question 13

integration

Answer 13

2 opposite signals, outcome is the integration of those.

Question 14

localised response

Answer 14

message remover is close to the message producer