The molecular clock has limited usefulness for estimating divergence times among species in part due to the saturation of DNA sequences. This occurs because
A) DNA sequences are unable to revert back to previous allelic states.
B) the variation in the substitution rate between closely related lineages prevents accurate estimation of divergence time.
C) variation in population sizes among lineages changes the effect of genetic drift.
D) in highly diverged lineages, substitutions will occur at sites that have been substituted previously.

Question

Quizplus · Accepted Answer

Saturation occurs when nucleotide substitutions accumulate to the point where homoplasies (different nucleotides at the same site) begin to occur due to convergent or parallel evolution. This, in turn, leads to an underestimation of the true evolutionary distance between two lineages. In highly diverged lineages, sites that have undergone multiple substitutions will have become saturated, and thus result in errors in estimating divergence times.

The Molecular Clock Has Limited Usefulness for Estimating Divergence Times