Gene Regulation: The Operon

Question 1

the functioning unit of DNA consisting of a cluster of genes under the control of single promoter; several structural genes arranged under a common promoter and regulated by a common operator

Answer 1

operon

Question 2

T/F the regulators of a given operon are not necessarily coded for by that protein

Answer 2

T

Question 3

a nucleotide sequence that enables a gene to be transcribed; recognized by RNA polymerase which then initiates transcription

Answer 3

promoter

Question 4

a segment of DNA to which a repressor binds

Answer 4

operator

Question 5

the genes that are co-regulated by the operon

Answer 5

structural genes

Question 6

a constantly expressed gene which encodes for repressor proteins

Answer 6

regulatory gene

Question 7

proteins that suppress transcription of a gene in response to an external stimulus

Answer 7

repressors

Question 8

proteins that increase transcription of a gene in response to an external stimulus

Answer 8

activators

Question 9

(small molecule) can displace a repressor (protein) from the operator site, resulting in activation of operon

Answer 9

inducers

Question 10

can bind to the repressor to allow its binding to the operator site

Answer 10

corepressor

Question 11

control of an operon is a type of ____________ that enables organisms to regulate the expression of various genes depending on environmental condition

Answer 11

gene regulation

Question 12

when an inducer is present, it binds to the repressor and makes it unable to bind to the operator, which allows for expression of the operon

Answer 12

negative inducible operon

Question 13

What type of operon is the lac operon?

Answer 13

negative inducible operon

Question 14

what is the inducer molecule in the lac operon?

Answer 14

allolactose

Question 15

corepressors are bound by the repressor protein which causes a conformational change to the active site so the activated repressor protein binds to the operator and prevents transcription

Answer 15

negative repressible operon

Question 16

what type of operon is the trp operon

Answer 16

negative repressible operon

Question 17

activator proteins are normally unable to bind to the DNA; when an inducer is bound by the activator protein, it undergoes a change in conformation so that it can bind to the DNA and activate transcription

Answer 17

positive inducible operon

Question 18

activator proteins are normally bound to the DNA segment; when an inhibitor (corepressor) is bound by the activator, it is prevented from binding the DNA which stops activation and transcription of the system

Answer 18

positive repressible operon

Question 19

codes for the enzyme B-galactosidase which breaks B-galactoside into its component sugars

Answer 19

lac Z

Question 20

codes for the B-galactoside permease, a membrane-bound protein constituent of the transport system

Answer 20

lac Y

Question 21

codes for B-galactoside transacetylase, an enzyme that transfers an acetyl group from Acetyl-CoA to B-galactosides

Answer 21

lac A

Question 22

the lac repressor is inactivated by _____________________ where inducer binding changes the properties of the DNA binding site

Answer 22

allosteric interaction

Question 23

What are the repressor’s two binding sites?

Answer 23

one for the operator DNA and one for the inducer

Question 24

describe the lac operon mechanism involving glucose.

Answer 24

glucose is a better energy source than lactose so there’s no need to turn the operon on if glucose is available

Question 25

cAMP-CAP protein complex serves as a ______________ to induce transcription

Answer 25

positive regulator

Question 26

when does cAMP begin to accumulate in the cell?

Answer 26

when glucose levels drop

Question 27

signaling molecule that is involved in glucose and energy metabolism in E.coli

Answer 27

cAMP

Question 28

what happens when cAMP binds to the CAP

Answer 28

the complex binds to the promoter region that switch on the genes for processing of alternative energy source

Question 29

what is the trp operon?

Answer 29

it has 5 genes that E.coli can use to synthesize tryptophan when it is not available in the environment

Question 30

What happens to the trp operon when tryptophan is absent?

Answer 30

the repressor can't bind to the operator so the operon is active and tryptophan is synthesized