Question

A certain segment of DNA can be used as a molecular clock. Its rate of mutation is one mutation per 15 million years. Examine the DNA segments from two different species: Species A: GTTGAGCTAGTATGGACC Species B: GATAAGCTAGTAAGGTCA Using this example, explain how this information can be used to determine how long ago these two species shared a common ancestor. Be sure to answer this question in paragraph form using complete sentences.

Answer 1

We can use these two DNA segments to roughly estimate how many years ago the species shared a common ancestor. First, we can count the number of differences separating segment a from segment b. Because Species B has 5 differences when compared to Species A, we see that as 5 different mutations that happened, or errors when copying the DNA. If there was one mutations per 15 million years, this means these two species shared a common ancestor around 75 million years ago. Hope I helped!