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Tweaking the Experiment
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First Experiment



1

The purpose of the sonication step is to
A)Stop conjugation
B)Hydrolyze β-ONPG
C)Break open the bacterial cells
D)Denature the F factor
2

If the addition of lactose was accidentally omitted, how would the results have been affected?
A)There would have been no effect on the results.
B)In the mated strain, there would have been less than 1%?β-galactosidase activity rather than 220%.
C)In the original mutant strain, there would have been less than 1% β-galactosidase activity instead of 100%.
D)In the mated strain, there would have been 100% β-galactosidase activity instead of 220%.
3

If the original mutation that caused constitutive expression had been in the operator site instead of the lacI gene, how would the results have been affected?
A)There would have been no effect on the results.
B)In the mated strain, there would have been 220% β-galactosidase activity in the absence of lactose.
C)In the mated strain, there would have been 100% β-galactosidase activity in the absence of lactose.
D)In the original mutant strain, there would have been < 1% β-galactosidase activity in the absence of lactose.
4

If β-ONPG was accidentally omitted from this experiment, how would the results have been affected?
A)There would have been no effect on the results.
B)There would have been yellow color in all four tubes.
C)There would have been yellow color in the first two tubes only.
D)There would not have been yellow color in any of the four tubes.
5

The absence or presence of lactose has no effect on the original mutant strain because
A)It already makes a large amount of lactose.
B)It cannot transcribe the operon under any conditions.
C)The operator site is defective.
D)The repressor protein is defective.







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