Question

In a genetics lab, Kim and Maria infected a sample from an E. coli culture with a particular bacteriophage. They noticed that most of the cells were lysed, but a few survived. The survival rate in their sample was about 1 × 10−4. Kim was sure the bacteriophage induced the resistance in the cells, while Maria thought that resistant mutants probably already existed in the sample of cells they used. Earlier, for a different experiment, they had spread a dilute suspension of E. coli onto solid medium in a large petri dish, and, after seeing that about 105 colonies were growing up, they had replica-plated that plate onto three other plates. Kim and Maria decide to use these plates to test their theories. They pipette a suspension of the bacteriophage onto each of the three replica plates. What should they see if Kim is right? What should they see if Maria is right?

Answer 1

We can study mutations of the bacteria by fluctuation test and replica plating. In the replica planting, we grow various cultures on one plate and then inoculate these microorganisms into one or several secondary plates which contain various selective growth media. The goal of replica plating is to compare the master plate with secondary plates, in order to screen for a certain

phenotype

. If we presume that Kim is right then the bacteriophage can induce mutations in bacteria causing them to become resistant. Probability is 1 in 10,000 bacteria. If we have 100,000 bacteria, we could expect that about 10 of them express this mutation. Resistant bacteria will be randomly disseminated on the three secondary plates. However, if we presume that Maria is right and that 1 in 10,000 bacteria is already resistant to certain bacteriophage, we could expect that around ten out of 100,000 bacteria will appear at the same areas on three secondary plates.

Step-by-step explanation:

Note: Answer is hightlighed in bold and also these are not written in my own words I got the answer from Quizlet.