Chapter 8 Part 3

Question 1

why can’t every gene be turned on?

Answer 1

because it requires energy

Question 2

_____ are expressed at a fixed rate

Answer 2

constitutive genes

Question 3

other genes that are expressed only as needed:

Answer 3

• inducible genes
• repressible genes
• catabolite repression

Question 4

inhibits gene expression and decreases enzyme synthesis

Answer 4

repression

Question 5

repressions are mediated by ____, proteins that block transcription

Answer 5

repressors

Question 6

default position of repressible gene is ___

Answer 6

on

Question 7

____ turns on gene expression

Answer 7

induction

Question 8

induction is initiated by an ___

Answer 8

inducer

Question 9

default position of an inducible gene is ___

Answer 9

off

Question 10

segment of DNA that controls transcription of structural genes

Answer 10

operator

Question 11

set of operator and promoted sites and the structural genes they control

Answer 11

operon

Question 12

segment of DNA where RNA polymerase initiates transcription of structural genes

Answer 12

promoter

Question 13

in an _____, structural genes are not transcribed unless an inducer is present

Answer 13

inducible operon

Question 14

in an inducible operon, structural genes are not transcribed unless an ___ is present

Answer 14

inducer

Question 15

in the absence of lactose, the ___ binds to the operator, preventing transcription

Answer 15

repressor

Question 16

in the presence of lactose, ___ binds to the repressor, the repressor cannot bind to the operator and transition occurs

Answer 16

lactose (inducer)

Question 17

regulates the process of an inducible operon

Answer 17

regulatory gene

Question 18

what DNA sequence produces our repressor protein?

Answer 18

regulatory gene

Question 19

during a repressor inactive, the operon is __

Answer 19

on

Question 20

in ____, structural genes are transcribed until they are turned off

Answer 20

repressible operons

Question 21

excess ___ is a co-repressor that binds and activates the pressor to bind to the operator, stopping tryptophan synthesis

Answer 21

tryptophan