Exam 3: Lac Operon

Question 1

Laci

Answer 1

Repressor

Question 2

LacP

Answer 2

Promoter

Question 3

LacO

Answer 3

Operator

Question 4

LacZ

Answer 4

Beta-galactosidase

Question 5

LacY

Answer 5

Lactose permease

Question 6

LacA

Answer 6

transacetylase

Question 7

O^C

Answer 7

constitutive operator

Question 8

I^S

Answer 8

super repressor

Question 9

what type of operon is the Lac operon?

Answer 9

negative inducible

Question 10

When allolactose binds to the regulator protein…

Answer 10

it makes the repressor inactive

Question 11

Cis mutation effect

Answer 11

promoter and operator can only affect its gene

Question 12

Trans mutation effect

Answer 12

Repressor protein (laci) can transfuse across genes

Question 13

Strongest to weakest mutations

Answer 13

P- > OC > IS > I+ > I-

Question 14

When can DNA-binding proteins not bind?

Answer 14

When the DNA changes its sequence, LacOC, or if the protein changes its binding motif, LacI-

Question 15

What 2 things need to happen for the lac operon to become active?

Answer 15

1. Low glucose levels so that CAP can be activated and bind to the operon
2. Lactose is present

Question 16

The minimum function of the lac operon at high levels of glucose

Answer 16

Low levels of cAMP, cAMP binds to CAP less which leads to less efficient polymerase bidning to DNA and transcription rate is low of lac operon

Question 17

Maximum function of lac operon at low or no levels of glucose

Answer 17

High levels of cAMP, cAMP binds to CAP, CAP-cAMP binds to DNA, and there is efficient polymerase binding to lac operon, and glucose and produced from lactose

Question 18

Catabolite repression

Answer 18

Using glucose when availiable and repressing the metabolite of other sugars

Question 19

Why is the CAP-cAMP mechansim a positive control mechanism?

Answer 19

The positive effect is activated by CAP, and cAMP binds to it, and they bind as a complex to a site slightly upstream of the lac gene promoter

Question 20

The [cAMP] ___ when available glucose increases

Answer 20

decreases

Question 20

ZERO transcription

Answer 20

LacP-, LacZ-, LacY-

Question 21

CONSTITUTIVE transcription

Answer 21

lacI-, LacOC