SAT Subject Biology Practice Question 459: Answer and Explanation

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Question: 459

9. A population of ampicillin-resistant bacteria (Strain 1) is grown in a laboratory and is infected with a virus. The bacterial population begins to decline as the virus initially goes through the lytic cycle, then rebounds as the virus integrates into the bacterial chromosome to begin the lysogenic cycle.

The bacteria reproduce normally until they are heat-shocked. The rapid increase in temperature causes the virus to remove itself from the bacterial genome and enter the lytic cycle. Within several hours all bacteria are dead and a free virus is found in high concentration in the bacterial growth medium.

This free virus is used to infect a population of bacteria that is sensitive to ampicillin (Strain 2). After the expected decrease and rebound of this bacterial population (as above), the rebounded population was found to be ampicillin-resistant.

Which of the following increase genetic diversity in bacteria?

I. Conjugation

II. Transformation

III. Cros

A. I only
B. I and II only
C. III only
D. II and III only
E. I, II, and III

Correct Answer: B


B Remember the I, II, III technique! Again, you need to know the definitions of these terms. Conjugation is the transfer of DNA between two strains of bacteria and leads to genetic diversity. Therefore, option I is true, and choices C and D can be eliminated. Transformation means the bacteria acquire DNA from the environment; this also leads to genetic diversity. Because option II is also true, choice A can be eliminated. Crossing over is a phenomenon associated with meiosis, which bacteria do not undergo. Option III is false, eliminating choice E.

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