Question 33

[yikang_xu4881]

33. Which of the following best accounts for the reason a researcher would choose to perform a negative selection as opposed to a positive selection test?

1. The researcher wants to characterize the genome of a non-mutant wild type bacteria. [x]
2. The researcher wants to characterize the genome of mutant bacteria. [x]
3. The researcher wants to isolate non-mutant wild type bacteria. [x]
4. The researcher wants to isolate mutant bacteria.

Consulting any bio textbook will tell you that the goal of negative selection is to isolate mutants that DO NOT grow under the selective condition!!!

otherwise why would biologists perform mutagenesis and devise novel ways to select for MUTANTS if their goal is just to isolate wildtype?

[admin]

I will first respond by just looking at what can be gleened from the passage (MCAT-level understanding) then I'll dig a bit deeper to provide more understanding (more academic than necessary).

Keeping in mind that this passage covers advanced level information regarding which the AAMC would not expect a student to have prior knowledge, let's begin by focusing on the passage. P2 suggests that positive selection grows mutants while P3/4 suggests that negative selection grows both mutants and wild type. Staying at the level of the passage, the only answer choice consistent with the above would be that the advantage of negative selection is the additional growth of wild type bacteria.

Now it seems that you wish to explore this deeper which is fine from a curiousity standpoint.

[admin]

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