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.

Answer 1

Species A: G T T G A G C T A G T A T G G A C C
Species B: G A T A A G C T A G T A A G G T C A
Differences: 1 1 1 1 1

In comparing the species, I noticed 5 differences. I noted the differences using 1.

Since the problem states that 1 mutation occurs per 15 million years, it is safe to say that the two species shared a common ancestor 75 million years ago.

5 mutations * 15million yrs/mutation = 75 million years.