GENETICS CHAPTER 14

1)In negative control what molecule would you expect to find bound to the operator if there is no transcription?,

B)repressor

2)You want to design a repressor protein mutant. Which protein domain is the best target for preventing binding of the corepressor?

B)allosteric domain

3)The presence of which combination of molecules would lead to active transcription of an operon?

E)activator + inducer

4)In the lac operon what acts as the inducer?,

C)allolactose

5)The enzyme β-galactosidase catalyzes what reaction?

C)lactose → galactose + glucose

6)A bacterium is unable to transport lactose into the cell to be broken down. Which gene is likely mutated in this bacterium?

B)lacY

7)Which region of the lac operon would you target if you want to disrupt the -10 and -35 consensus sequences?

D)lacP

8)In the presence of glucose where is the lac repressor bound?,

B)lacO

9)Which structural gene of the lac operon can be mutated without affecting the cell's ability to break down lactose?

C)lacA

10)Which of the following can be mutated to result in constitutive expression from the lac operon?

C)lacO and lacI

11)Which of the following mutants are noninducible?

A)lacIS

12)Which of these haploid strains produces β-galactosidase constitutively but does not produce permease?

E)I - P+ O+ Z+ Y -

13)Which of these haploid strains produces permease but does not produce β-galactosidase?

B) I+ P+ O+ Z - Y+

14)During the attenuation of the trp operon which stem loop leads to polycistronic mRNA synthesis during tryptophan starvation?,

D)2-3 (antitermination) stem loop

15)In the absence of tryptophan __________.,

A)the inactive repressor cannot bind trpO, so operon gene transcription occurs

16)Which sigma factor encoded by the rpoH gene, is active at high temperatures?

B)σ32

17)Which enzyme is responsible for integration of a temperate phage into a host genome?

C)integrase

18)Which region of the λ phage genome enables the linear chromosome to circularize when it enters a host cell?

A)cohesive (cos) site

19)If you wanted to prevent a cell from entering the lysogenic pathway which gene controlled by PRM would you target for inactivation?,

C)cI

20)In λ phage which protein, the product of the cI gene, blocks the transcription required to initiate the lytic cycle?,

B)repressor

21)What would be the phenotype of an int− λ mutant?

C)The phage would be able to enter the lytic cycle, but would not be able to lysogenize.

1)Regulation of transcription of bacterial genes takes place at which two levels?

initiation and amount

2)What are the two active sites or "domains" on a repressor protein?

DNA-binding and allosteric

3)If a corepressor is inhibited what effect would you expect to see in the operon?,

Transcription will occur.

4)Which proteins facilitate RNA polymerase binding at promoters?

activator proteins

5)Catabolite repression refers to the repression of the lac operon in the presence of which catabolite?

glucose

6)Binding of which complex increases the ability of RNA polymerase to transcribe the lac operon?

CAP-cAMP

7)Which enzyme is the product of the lacZ gene?

β-galactosidase

8)Which part of the lac operon is cis-dominant?

lacO

9)Which part of the lac operon produces a regulatory protein that is trans-acting?

lacI

10)When both glucose and lactose are available in the growth medium the presence of which molecule is capable of inducing basal transcription of the lac operon?,

cAMP

11)For each of the following E. coli partial diploid strains indicate whether expression of β-galactosidase and permease is inducible (I) constitutive (C), or negative (no product made) (N). Assume glucose levels are very low. Which of the strains are able to use lactose as their sole carbon source?

(go back to actual review. look at table) Only strain c is able to use lactose as its sole carbon source. Strains a and d never make permease and strain b never makes β-galactosidase.

12)In the trp operon where is the attenuator region located?,

trpL

13)Which molecule functions as the corepressor in the trp operon?

tryptophan

14)What are the names of the three possible alternative stem loops that can form in mRNA?

pause, antitermination, and termination

15)Mutations of trpL decrease the efficiency of transcriptional regulation by disrupting the formation of which stem-loop structure?

3-4 (termination) loop

16)Bacteria grown at 45°C initiate expression of which two types of proteins?

heat shock and chaperone

17)Antisense control of translation involves the regulation of which enzyme produced by bacterial insertion sequence IS10?

transposase

18)The genetic switch controlling whether a bacterium enters the lytic or lysogenic cycle relies on the binding of which two proteins?

cro and λ repressor

19)What is the process by which a bacterium switches from a lysogenic to lytic cycle?

induction

20)What protein cleaves the λ repressor monomers to inactivate the repressor protein and is activated by DNA-damaging agents?,

RecA

1)Most of the regulation of gene expression in bacteria occurs at the ________ level.

transcriptional

2)Changing conformation at the active site as a result of binding a substance at a different site is known as ________.

allostery

3)Expression of a(n) ________ alters gene transcription in E. coli by activating transcription of specialized heat stress response genes.

alternative sigma factor

4)Bacterial translation is inhibited by ________ RNA which is complementary to a portion of a specific mRNA.,

antisense

5)In λ phage entry into the ________ cycle requires transcription of late genes.,

lytic