Chapter 16

Question 1

structural genes

Answer 1

encode proteins

Question 2

operon

Answer 2

regulates the expression of the structural genes by controlling transcription
includes a gene, promotor, and operator

Question 3

regulator

Answer 3

has its own promoter and is transcribed into short mrna

Question 4

negative control

Answer 4

regulatory protein is a repressor binding to dna and inhibiting transcription

Question 5

positive control

Answer 5

regulatory protein is activator and stimulates transcription

Question 6

inducible operons

Answer 6

transcription is off

Question 7

repressible operons

Answer 7

transcription is normally on

Question 8

inducer

Answer 8

small molecule that allows transcription of a negatives inducible operon to be turned on and binds to repressor protein

Question 9

what does the binding of the inducer cause

Answer 9

alters the shape of the repressor and prevents it from binding to dna

Question 10

allosteric proteins

Answer 10

changes shape when binding to another molecule

Question 11

what happens when inducer is absent

Answer 11

the regulator protein is a repressor and binds to the operator and prevents transcription of the structural genes

Question 12

at happens when inducer is present

Answer 12

it binds to the regulator, making the regulator unable to bind to the operator and transcription takes place

Question 13

negative repressible operson

Answer 13

• transcription normally takes place and must be turned off or repressed
• repressor is an inactive form and can’t bind to the oeprator

Question 14

corepressor

Answer 14

makes repressor active and binds to repressor to make it capable of binding to the operator and prevent transcription

Question 15

what happens in positive transcriptional control

Answer 15

regulatory protein involved is an activator and binds to dna to activate transcription

Question 16

inducible operons / repressible operons

Answer 16

inducible: operons are off and must be turned on and the repressible operon is when transcription is normally on and must be turned off

Question 17

why type of operon is the lac operon

Answer 17

negative inducible operon - when lactose is present some of it is converted to allolactose which binds to repressor and causes the repressor to be released from the operator

Question 18

cis acting operons

Answer 18

able to controls the expression of genes only on the same piece of dna