A number of mutations affect the expression of the lactose operon in E. coli. Complete the table given below. Use +/plus to indicate that the enzyme is synthesized at greater than basal levels, and -/minus to indicate that the enzyme is not synthesized. Use only - and +. Don't be creative and use your own symbols or they will be counted as incorrect. And, don't leave any blank!
Will there be expression of the gene ->
b-galactosidase lacZ (not present)
b-galactosidase lacZ (present)
Permease lacY (not present)
Permease lacY (present)
I+O+Z+Y+
IsO+Z+Y+
I+OcZ-Y+
I-O+Z-Y+/F'O+Z-Y- (hint: no normal I)
IsZ+Y+/F' I-Z+Y+
6. The lac operon is optimally expressed
a. in the absence of both lactose and glucose
b. in the absence of lactose and the presence of glucose
c. in the presence of lactose and the absence of glucose
d. in the presence of both lactose and glucose
e. in none of the above
7. A lac Z- mutant would have a similar phenotype as which of the following?
a. lac Is
b. lac I-
c. lac Oc
d. lac A-
e. CAP-
8. Which of the following functions in trans?
a. Lac O
b. Trp R protein
c. Lac I protein
d. CAP
e. b, c, and d
9. When an E coli cell is exposed to glucose, how does this effect the regulation of the lac operon by CAP?
a. cAMP binds to CAP and transcription is increased.
b. cAMP binds to CAP and transcription is decreased.
c. cAMP does not bind to CAP and transcription is increased.
d. cAMP does not bind to CAP and transcription is decreased.