Topic 8

Question 1

What are constitutive genes?

Answer 1

genes that are continuously expressed in most cells and are essential components of almost all living cells

Question 2

What is positive regulation?

Answer 2

activator turns on genes to allow transcription

Question 3

What is negative regulation?

Answer 3

repressor binds operator and there is no transcription

Question 4

What is trans regulation?

Answer 4

encoded by genes somewhere else in the genome

Question 5

What is cis regulation?

Answer 5

DNA segments close to the genes they regulate

Question 6

How do allosteric effectors play into gene regulation?

Answer 6

bind regulatory proteins often to regulate transcription

Question 7

What is positive control?

Answer 7

product of a regulatory gene is required to initiate the expression of one or more genes

Question 8

What is negative control?

Answer 8

product of a regulatory gene is required to turn off the expression of one or more genes

Question 9

How does an inducer work in a negative control gene regulation system?

Answer 9

Inducer binds repressor that is normally on DNA therefore allowing transcription to occur

Question 10

How does an inducer work in a positive control system?

Answer 10

inducer binds activator to allow transcription

Question 11

How does a co-repressor work in a negative control system?

Answer 11

naked repressor cannot bind to regulator protein binding site without the co repressor, so the addition of the co repressor allows for repression

Question 12

How does a co-repressor work in a positive control system?

Answer 12

addition of a co-repressor to an activator displaces it not allowing transcription to occur

Question 13

What are operons?

Answer 13

unit made up of linked genes which is thought to regulate other genes responsible for protein synthesis

Question 14

What is an inducible operon?

Answer 14

turned off until induced

Question 15

What is a repressible operon?

Answer 15

turned on until repressed

Question 16

What is the lac operon in E. Coli?

Answer 16

produces enzymatic machinery needed to metabolize lactose-transcription depended on lactose as sole energy source

Question 17

What type of operon is the Lac Operon?

Answer 17

Inducible

Question 18

What is the allosteric regulator of the lac operon?

Answer 18

allolactose

Question 19

What is the I gene?

Answer 19

trans regulation-repressor gene

Question 20

What is the O site?

Answer 20

site of inhibitor binding-in cis regulation

Question 21

What is the P site?

Answer 21

site of RNA pol binding-promoter

Question 22

What happens if there is a mutation in any of the structural genes of the lac operon?

Answer 22

cannot metabolize lactose even if operon is expressed

Question 23

What happens if the I gene is mutated?

Answer 23

cannot turn off expression of LacO

Question 24

What happens if the O gene is mutated?

Answer 24

cannot turn off expression

Question 25

How did they tell whether or not the LacO mutations acted in cis or trans effect

Answer 25

add F+ plasmid where they had extra copies of LacO

Question 26

What is the solution to the negative feedback issue?

Answer 26

using chemical analogs-to induce LacO but not be metabolized and that can be metabolized but not induce LacO

Question 27

What happened when there were two copes of the structural genes in the cell?

Answer 27

twice as much enzyme activity

Question 28

What was determined about the operator from this experiment?

Answer 28

it can only act in cis-if there are two strands it cannot act on other strand

Question 29

What happens if there is a mutated operator but functional repressor?

Answer 29

will be expressed

Question 30

How does the I gene regulate gene expression?

Answer 30

acts in cis and trans

Question 31

What is the structure of the lac repressor?

Answer 31

tetramer

Question 32

How does the tetramer block transcription?

Answer 32

binds more than one operator which means it forms a loop and blocks activity RNA

Question 33

What is the Is mutation?

Answer 33

dominant mutation where the repressor could not bind the inducer and there is permanent repression

Question 34

What is the metabolites that impact the lac operon?

Answer 34

CAP and cAMP

Question 35

What do the CAP and cAMP do to the operon?

Answer 35

activates operon

Question 36

Why is the ara operon cool?

Answer 36

AraC serves as an activator and repressor depending on presence or absence of inducer