Final answer:
Molecular clocks use genes that either evolve very slowly or rapidly to estimate evolutionary divergence times. Both types of genes can be effective, depending on whether the focus is on long-term or recent evolutionary events.
Step-by-step explanation:
Molecular clocks utilize well-conserved or poorly conserved genes to estimate the time since related species diverged from a common ancestor. For studying recent evolutionary events, either a very well-conserved gene or a poorly conserved gene could be utilized as a molecular clock tool. Well-conserved genes typically change slowly, suitable for studying divergence over longer periods.
On the other hand, poorly conserved genes change more rapidly and can be used to study more recent evolutionary events. However, it is essential to note that the mutation rate can vary, and relying on a fixed molecular clock might be misleading. Multiple genes from different DNA regions should be used together for increased accuracy in molecular clocks.