Molecular clocks are more reliable when _.
The correct answer and explanation is:
Molecular clocks are more reliable when the mutation rate is relatively constant over time across different species.
The concept of molecular clocks is based on the idea that genetic mutations accumulate at a steady rate over time in a particular lineage. These mutations are usually neutral, meaning they do not affect the organism’s fitness. By counting the number of differences between two species’ genetic sequences, scientists can estimate how much time has passed since the species last shared a common ancestor.
However, the reliability of molecular clocks depends on several factors. First, if the mutation rate is constant and similar in related species, molecular clocks can provide more accurate estimates of divergence times. When the mutation rate varies significantly between species or evolutionary lineages, the molecular clock becomes less predictable, and the estimated divergence times can become erroneous.
Another factor is the calibration of the molecular clock. To be accurate, molecular clocks need to be calibrated against known fossil records or other well-established timelines. Without such calibration, molecular clock estimates could be off.
Additionally, different types of genes or genomic regions mutate at different rates. Some regions may evolve quickly, while others change more slowly. Molecular clocks that rely on faster-evolving genes may be more suitable for estimating recent divergence events, while slower-evolving genes may be more appropriate for studying deeper evolutionary timescales.
In summary, molecular clocks are more reliable when mutation rates are relatively constant across species and when they are calibrated with known timelines. The method’s accuracy can be improved by using appropriate genetic markers that evolve at rates suited to the time frame being studied.