Ch. 8 Part 2

Question 1

What is gene expression?

Answer 1

transcription of gene into mRNA
followed by translation of mRNA into protein

Question 2

What inhibits gene expression and decreases enzyme synthesis?

Repression is mediated by repressors. What is the function of repressors?

T/F Default position of a repressible gene is ON

Answer 2

Repression

block transcription

TRUE

Question 3

T or F Constitutive proteins are needed at the same level all the time

Answer 3

True

Question 4

Induction turns on ______ ______

Induction is initiated by substances that induce enzyme synthesis called what?

What is the default position of an inducible gene?

Answer 4

gene expression

Inducer

OFF

Question 4

what do Microbial genomes encode and how are they expressed?

Answer 4

1. proteins that are not needed all the time
2. expressed only as needed.

Question 5

_____________ genes need to be induced to be regulated while ___________ genes need to be repressed for regulation?

Answer 5

inducible genes
repressible genes

Question 6

1. what is the promoter in the operon model of gene expression?
2. segment of DNA that controls transcription? (located downstream of promoter)
3. what do operons include?

Answer 6

1. segment of DNA where RNA polymerase initiates transcription
2. operator
3. set of operator and promoter sites, and
   structural genes they control

Question 7

What is a collective term for inducers and repressors?

How do effectors affect transcription indirectly?

Answer 7

Effectors

by binding to specific DNA-binding
proteins

Question 8

what is the repressor’s role and what is it called?

Answer 8

inhibitory, so it is called negative control

Question 9

What do repressor molecules bind to?

This protein becomes active and binds to what?

Answer 9

allosteric repressor protein

the Operator (region of dna near promoter)

Question 10

In an inducible operon structural genes are only transcribed if what?

Answer 10

an inducer is present

Question 11

In the absence of __________, the repressor (product of the gene) binds to the operator, preventing transcription

Answer 11

lactose

Question 12

In the inducible operon, the repressor is __________ while the operator is __________.

Answer 12

repressor is active

operon off

Question 13

In the lac operon of E. coli what is needed to metabolize lactose?

Where are the structural genes for these enzymes (Z, Y, and A)?
- is their transcription regulated separately or together?

Answer 13

Three enzymes encoded by the lac operon

adjacent on the chromosome
- TOGETHER

Question 14

The control region includes what 2 things? What happens at each?

Answer 14

1. Promoter: where transcription begins
2. Operator: stop or go signal

Question 15

In repressible operons, structural genes are transcribed until when?

Answer 15

they are turned off

Question 16

1. E.g. trp is the operon of which bacteria in the repressible operon?
2. What is the corepressor that binds and activates the repressor to bind to the operator?

Answer 16

1. E. coli
2. Excess tryptophan

Question 17

INDUCIBLE OPERON MODEL OF GENE EXPRESSION

In the presence of lactose, what binds to the repressor?

What does this cause?

Answer 17

A metabolite of lactose:
allolactose (inducer)

the repressor can’t bind to the operator and transcription
occurs

Question 18

T/F operons are negative regulation

Answer 18

TRUE

Question 19

POSITIVE REGULATION

Catabolite repression inhibits cells from what?

Answer 19

using carbon sources other than glucose

Question 20

What is the result of the excess tryptophan corepressor?

Answer 20

stops the synthesis of tryptophan

Question 21

POSITIVE REGULATION

When does Cyclic AMP (cAMP) build up in a cell?

Answer 21

When glucose isn’t available

Question 22

Define alarmone and give an example of one?

Answer 22

a chemical that promotes a cell’s response to environmental or
nutritional stress
- cAMP

Question 23

POSITIVE REGULATION

cAMP binds to the ________ _________ ________(CAP) that in
turn binds the lac promoter,
initiating _____________ and
allowing the cell to use _________.

Answer 23

Catabolic activator protein

transcription

lactose