SAT Subject Biology Practice Question 168: Answer and Explanation

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Question: 168

18. A female chimpanzee recently gave birth to an infant while in captivity. Because the paternity of the infant is unclear, scientists tested the DNA from two male chimpanzees, along with the female and infant. The resulting electrophoresis gel is shown.

Which labeled DNA fragment is largest?

A. 1
B. 2
C. 3
D. 4
E. 5

Correct Answer: A

Explanation:

Larger DNA fragments travel through an agarose gel at a slower rate than smaller fragments. Fragment 1 is closest to the wells where the DNA was originally inserted. It has traveled the shortest distance and is therefore the largest.

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