Question

What information is needed to calibrate a molecular clock and use it to estimate the time that has passed since two species shared a common ancestor?

A. You need the gene sequences for both of the species, and you must know the ratio of radioactive isotopes to stable products in the DNA of each species.
B. You need to know the gene sequences for both of the taxa plus those of several related taxa. For at least three pairs of those taxa, you need good estimates of divergence times based on the fossil record.
C. You need the gene sequences for both of the species, along with those of several related taxa.
D. You only need the gene sequences for both of the species.

Answer 1

To calibrate a molecular clock, the gene sequences of both species and several related taxa are needed, plus divergence times from the fossil record for three pairs of taxa to establish mutation rates.

Step-by-step explanation:

To calibrate a molecular clock and use it to estimate the time that has passed since two species shared a common ancestor, it is necessary to know the gene sequences of both species involved.

However, to get an accurate calibration, additional information is required.

Specifically, you also need the gene sequences of several related taxa, and importantly, good estimates of divergence times for at least three pairs of taxa based on the fossil record.

The combined data from molecular clocks and the fossil record allows for the establishment of a mutation rate that is then applied to the molecular data to estimate divergence times.

Once the gene sequences are obtained, they can be compared with known sequences in databases through computational tools to align and analyze the sequences.

This analysis gives the percentage of sequence identity or sequence homology that correlates with evolutionary distance, thus providing a time estimate since the two species diverged from their common ancestor.