McMaster University

BIO 2EE3

CHAPTER 11

1)The expression of genes required for biofilm formation occurs only after a cell has attached to a surface that is suitable for biofilm development. What is this type of gene expression called

1. 1. Feedback inhibition
   2. Attenuation
   3. Repression
   4. Inhibition
   5. Induction

2. What is an effector molecule?
   1. A small RNA molecule that inhibits translation of mRNA
   2. An activator protein for gene expression
   3. A small molecule that binds to the operator region of a gene
   4. A protein that binds to an operator region of a gene
   5. A small molecule that binds to an enzyme to regulate its activity

3. Which of these controls the expression of the lac operon?
   1. Both repression and activation mechanisms
   2. An activator protein only
   3. An attenuation mechanism
   4. Both repression and attenuation mechanisms
   5. A repressor protein only

4. Isopropyl β-d-1- thiogalactopyranoside (IPTG), a lactose analog, acts as an inducer of the lac operon. What is its mode of action?
   1. It binds to the operator to enhance transcription initiation
   2. It activates the enzyme β-galactosidase
   3. It functions as a co-activator for gene expression
   4. It inactivates the LacI repressor protein
   5. It binds the RNAP for enhanced binding to the promoter

5. Which component of the two-component regulatory system frequently senses changes in the external environment?
   1. Activator protein
   2. Response regulator
   3. Transport protein
   4. Repressor protein
   5. Histidine kinase

6. Which autoinducer is used by many Gram-negative bacteria?
   1. A metabolic intermediate
   2. An activator protein
   3. A homoserine lactone derivative
   4. Allolactose
   5. A repressor protein

7. The term for a large group of genes whose expression is under the control of a single regulatory system
   1. Biome
   2. Regulon
   3. Super operon
   4. Operon
   5. Transcriptome

8. What is a “reporter gene”?
   1. A gene that is expressed under adverse environmental conditions
   2. The fusion of a gene of interest to a regulatable promoter
   3. A gene whose product can easily be measured
   4. The fusion of a promoter region of interest to a gene whose product can easily be measured
   5. The fusion of two different structural genes

9. Which is true of catabolite repression?
   1. It results in increased growth rates
   2. It results in decreased growth rates
   3. It occurs because of the toxicity of certain chemicals
   4. It only occurs when lactose is present
   5. It results in diauxic growth

10. What does sigma factor helps the RNA polymerase do?
    1. Identify the promoter region of a gene
    2. Bind to activator proteins
    3. Release from the transcribed DNA
    4. Attach the ribosomal subunits
    5. Assemble tRNA subunits

11. Expression of genes that are constitutive is
    1. Regulated by induction
    2. Regulated by repression
    3. Regulated by attenuation
    4. Regulated by activation
    5. Unregulated

12. During negative regulation of gene expression the repressor protein binds to the operator to inhibit transcription. What is the effector molecule that controls the activity of the repressor protein called?
    1. Corepressor
    2. Inducer
    3. Corepressor or inducer
    4. Activator
    5. Corepressor or activator

13. How will E. coli growing in a medium containing both lactose and glucose react?
    1. Neither compound will be utilized for growth
    2. One will sometimes be utilized
    3. By preferentially utilizing glucose first
    4. By utilizing both at the same time
    5. By preferentially utilizing lactose first

14. A mutation in the lacI gene results in an active repressor protein that can no longer bind allolactose. Which would be true of the phenotype of the mutant strain?
    1. It would repress β-galactosidase when lactose is present
    2. It would be constitutive for β-galactosidase expression
    3. It would be overexpress β-galactosidase when lactose is present
    4. It would overexpress LacZ
    5. It would be the same as the wild-type strain

15. Which of these is typically involved in a two-component regulatory system?
    1. Repressor protein and co-repressor
    2. A repressor protein and an inducer
    3. Repressor protein and an activator protein
    4. An activator protein and a co-activator
    5. Histidine kinase and a response regulator

16. Once the autoinducer excreted by Vibrio fischeri reaches a critical concentration, it is able to diffuse back into the cell. What is its next action?
    1. Be cleaved by a protease to produce luminescence
    2. Inactivate a transcriptional repressor to allow transcription of the lux genes
    3. Bind to the promoter to enhance transcription of the lux genes
    4. Bind to a transcriptional activator protein to activate transcription of the lux genes
    5. Bind to the bacterial luciferase to produce luminescence

17. Which of these is required for transcription that is regulated by positive control?
    1. Repressor protein
    2. Attenuator protein
    3. Activator protein
    4. DNA polymerase
    5. Inducer protein

18. Mutants that constitutively expressed β-galactosidase were placed into two different groups.

Where were the mutations for constitutive expression located

1. 1. In either the LacI or LacY genes
   2. In either the LacI gene or operator region
   3. In either the LacZ gene or operator region
   4. In either the LacZ or LacY genes
   5. In either the LacZ or LacI genes

19. When does repression of the lac operon occur?
    1. When allolactose binds to the operator region
    2. When allolactase binds to the repressor protein
    3. When allolactase binds to β-galactosidase
    4. When the repressor protein binds to the operator region
    5. When the repressor protein binds to the promoter

20. How is quorum sensing, a type of cell to cell communication, mediated?
    1. By two-component regulation
    2. By an induction mechanism
    3. By direct cell contact
    4. By chemical signaling
    5. By transfer of genetic information