What is the molecular clock and how is it used in evolutionary studies?

What is the molecular clock and how is it used in evolutionary studies?

• A. A fossil morphology-based clock uses morphological changes and assumes a constant rate.
• B. A method that uses the rate of genetic mutations to estimate divergence times; assumes a relatively constant mutation rate.
• C. A method that uses current population sizes to infer historical events.
• D. A method that compares protein folding patterns to date speciation.

Answer: (B)

The molecular clock is a method that uses the rate of genetic mutations to estimate when species diverged from a common ancestor. By comparing DNA or protein sequences, scientists count the differences and, assuming mutations accumulate at a roughly constant rate, convert those differences into time since separation. Calibration with independent data, like fossils or known divergence events, lets us translate the number of mutations into an actual age. This approach works best when the mutations are neutral and the rate is relatively stable across lineages, or can be modeled with relaxed clock methods. It’s used to build evolutionary timelines and test relationships inferred from other data. Other approaches described in the options focus on non-genetic data or different kinds of changes (morphology rather than sequence, population demographics rather than mutation rate, or protein folding patterns), so they don’t describe the molecular clock.

The molecular clock is a method that uses the rate of genetic mutations to estimate when species diverged from a common ancestor. By comparing DNA or protein sequences, scientists count the differences and, assuming mutations accumulate at a roughly constant rate, convert those differences into time since separation. Calibration with independent data, like fossils or known divergence events, lets us translate the number of mutations into an actual age. This approach works best when the mutations are neutral and the rate is relatively stable across lineages, or can be modeled with relaxed clock methods. It’s used to build evolutionary timelines and test relationships inferred from other data.

Other approaches described in the options focus on non-genetic data or different kinds of changes (morphology rather than sequence, population demographics rather than mutation rate, or protein folding patterns), so they don’t describe the molecular clock.