Question

A certain segment of DNA can be used as a molecular clock. Its rate of mutation is one mutation per 20 million years. Examine the DNA segments from two different species:
Species A: GTACCTAAGTTCACCGAATT
Species B: GAACCTAAGGGCACCGAACT

Using this example, explain how this information can be used to determine how long ago these two species shared a common ancestor.

Answer 1

Let's calculate the difference in nucleotides. The number of difference multiplied by rate of mutations will help to determine how long ago these two species shared a common ancestor.

Species A: GTACCTAAGTTCACCGAATT
Species B: GAACCTAAGGGCACCGAACT

These species differ in 4 nucleotides.
This number should be multiplied by the rate of mutations