Problem 10 - AP Psychology Premium Prep 2021

Question

Griffith was a researcher who coined the term transformation when he noticed that incubating nonpathogenic bacteria with heat-killed pathogenic bacteria produced bacteria that ultimately became pathogenic, or deadly, in mice. What caused the transformation in his experiment? (A) DNA from the nonpathogenic bacteria revitalized the heat-killed pathogenic bacteria. (B) Protein from the pathogenic bacteria was taken up by the nonpathogenic bacteria. (C) DNA from the pathogenic bacteria was taken up by the nonpathogenic bacteria. (D) DNA in the nonpathogenic bacteria turned into pathogenic genes in the absence of pathogenic bacteria.

Step-by-Step Solution

Answer

The correct answer is (C) DNA from the pathogenic bacteria was taken up by the nonpathogenic bacteria.

Step 1: Evaluate Option (A)

" DNA from the nonpathogenic bacteria revitalized the heat-killed pathogenic bacteria." This option suggests that nonpathogenic bacteria provided DNA to the heat-killed pathogenic bacteria which then revitalized them. This does not seem reasonable because once the bacteria are heat-killed, they cannot be brought back to life with a simple exchange of DNA.

Step 2: Evaluate Option (B)

" Protein from the pathogenic bacteria was taken up by the nonpathogenic bacteria." This option implies that proteins from the pathogenic bacteria were responsible for the transformation. However, Griffith's experiment showed that once heat-inactivated, the proteins in the pathogenic bacteria lost their ability to transform nonpathogenic bacteria. Therefore, this option is not correct.

Step 3: Evaluate Option (C)

" DNA from the pathogenic bacteria was taken up by the nonpathogenic bacteria." In Griffith's transformation experiment, the heat-killed pathogenic bacteria released their DNA into the surrounding environment. The nonpathogenic bacteria took up this DNA, which then provided them with genetic information required to become pathogenic. This explanation is consistent with the results of the experiment, making this the correct answer.

Step 4: Evaluate Option (D)

" DNA in the nonpathogenic bacteria turned into pathogenic genes in the absence of pathogenic bacteria." This option explains that pathogenic genes simply arose in the nonpathogenic bacteria on their own. This is not consistent with the conditions of the experiment, as the transformation was observed only when the nonpathogenic bacteria were in contact with heat-killed pathogenic bacteria. Answer: Based on the evaluation in Steps 1-4, the correct answer is \( \boxed{\textbf{(C)}\text{ DNA from the pathogenic bacteria was taken up by the nonpathogenic bacteria}} \).