1. You have discoveredan E. coli mutant that expresses a lac operon capprotein that is unable to bind cAMP. If you grew that mutant inglucose, lactose, IPTG, and glucose and lactose how would the?-galactosidase activity differ from an E. coli straincontaining a functional lac operon? What would happen if youtested an E. coli strain that contains a CAP protein thatcan bind DNA even in the absence of cAMP?

OneClass: 1. You have discoveredan E. coli mutant that expresses a lac operon capprotein that is unab...

1. The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/).

The possible answers indicate with a Êº+Êº or a Êº-Êº whether Î²-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)

Genotype C: Is Oc Z+/ FÊ¹ I + O+ Z+
KEY:

I+ = wild-type repressor
I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)

a. +,+ d. -,+

b. -,- e. cannot tell

c. +,-

2. The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/).

The possible answers indicate with a Êº+Êº or a Êº-Êº whether Î²-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)

Genotype D: I- O+ Z+/ FÊ¹ I- O+ Z+
KEY:

I+ = wild-type repressor
I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)

a. +,+ d. -,+

b. -,- e. cannot tell

c. +,-

3. The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/).

The possible answers indicate with a Êº+Êº or a Êº-Êº whether Î²-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)

Genotype E: I + O+ Z+/ FÊ¹ I + O+ Z+
KEY:

I+ = wild-type repressor
I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)

a. +,+ d. -,+

b. -,- e. cannot tell

c. +,-

ceruleantiger445

1. The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/).

The possible answers indicate with a Êº+Êº or a Êº-Êº whether Î²-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)

Genotype A: I + O+ Z+/ FÊ¹ I - O+ Z+

KEY:

I+ = wild-type repressor
I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)

a. +,+ d. -,+

b. -,- e. cannot tell for certain

c. +,-

2. The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/).

The possible answers indicate with a Êº+Êº or a Êº-Êº whether Î²-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)

Genotype B: I - Oc Z+/ FÊ¹ I - O+ Z-

KEY:

I+ = wild-type repressor

I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)

a. +,+ d. -,+

b. -,- e. cannot tell for certain

c. +,-

beigecaribou308

a. Suppose you isolated a mutation in the CRP gene that results in the production of a CRP protein that cannot bind cAMP. What effect would such a mutation have on expression of the lac operon in the presence versus the absence of lactose (assume that glucose is absent in both cases)?

Answer:

b. Suppose you isolated a different mutation in the CRP gene that results in the production of a CRP protein that binds to the CRP-binding site in the lac promoter even when there is no cAMP available. What effect would this mutation have on expression of the lac operon in the presence versus the absence of lactose, if glucose were also available in both cases?

Answer:

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