Prokaryotic Transcription Regulation (Lec 9)

Question 1

Constitutive Promoters

Inducible Promoters

Answer 1

Constitutive Promoters
- always switched on (continual transcription)

Inducible Promoters

• can be switched on
• subject to regulation

Question 2

Gene regulation proteins

• Operators

Answer 2

Proteins that bind to operators (DNA sequences ) close to or inside promoter DNA sequence

Operators
- Palindromic DNA sequences

Question 3

Operators

Answer 3

Palindromic DNA sequences to which regulatory proteins (Trans working) bind
up/ downstream of promoters
cis-working, only influence adjacent promoters

Question 4

Cis- working

Trans-working

Answer 4

Cis- working
-only influence adjacent promoters
Trans-working
- coded on another DNA molecule or on another part of the genome

Question 5

Regulatory Protein

Answer 5

bind to operators
trans-working
- gene not in physical contact with operator where it binds

Question 6

Main Regulation Mechanisms

Answer 6

Negative control

• repressor (regulatory protein)
• binding of repressor to operator = represses transcription

Positive control

• Activator (Regulatory protein)
• binding of activator to operator = activates transcription

Question 7

Small molecules [substrate or product of gene] modulate regulation mechanisms

Answer 7

Induction

• Transcription is induced/ switched on
• small molecule = INDUCER
• inactivate repressor protein (Negative control turned off)
• activates activator protein (+ control turned on)

Repression

• Transcription turned on
• Co-repressor
• inactivates activator (Positive control turned off)
• activates repressor (Negative control turned on)