Genetics: Analysis and Principles 4th Edition by Robert Brooker

Exercise 4

An absentminded researcher follows the protocol described in Figure 14.7 and (at the end of the experiment) does not observe any yellow color in any of the tubes. Yikes! Which of the following mistakes could account for this observation
A. Forgot to sonicate the cells
B. Forgot to add lactose to two of the tubes
C. Forgot to add -ONPG to the four tubes
FIGURE 14.7 Evidence that the lacI gene encodes a diffusible repressor protein. Starting material: The genotype of the mutant strain was lacI lacZ + lacY + lacA +. The merozygote strain had an F' factor that was lacI + lacZ + lacY + lacA +. The F' factor had been introduced into the mutant strain via conjugation.