SAT Subject Biology Practice Question 166: Answer and Explanation

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Question: 166

16. Scientists constructed a phylogenetic tree of modern lizard genera based on DNA sequences, shown below.

Lizards from which two genera most likely have the greatest number of noncoding DNA differences between them?

A. Aprasiaand Ophidiocephalus
B. Pygopusand Ophidiocephalus
C. Lialisand Aprasia
D. Pygopusand Pletholax
E. Lialisand Delma

Correct Answer: E


Because noncoding DNA differences do not affect phenotype, they accumulate at a constant rate over time. The longer two groups have evolved independently, the more noncoding differences there will be between them. The genera Lialis and Delma diverged from a common ancestor farthest back in time and would therefore be expected to have the greatest number of DNA differences.

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