Question

A certain segment of DNA can be used as a molecular clock. Its rate of mutation is one mutation per 10 million years. Examine the DNA segments from two different species: Species A: CTTAAGCTAGTAAGGACC Species B: CATAAGTTAGTAAGGTCC Using this example, explain how this information can be used to determine how long ago these two species shared a common ancestor.

Answer 1

Answer:

We would use the molecular clock in order to determine how long ago these species shared an ancestor. If we compare the DNA sequence of the two species, we would find that three mutations have taken place. Thus, 30 million years would have passed to evolve three mutations. Now, we divide 30 million by two because there are two species, and we can infer that they must have shared a common ancestor around 15 million years ago.

Answer 2

Answer:

The correct answer would be 30 million years.

The molecular clock is a technique used to determine the time when the two species diverged from a common ancestor. It uses the mutation rate to determine the same.

Mutation rate is the rate at which a number of mutations take place in a given unit time.

For example, the mutation rate in a given question is one mutation per 10 million years, that is, one nucleotide is mutated in 10 million years.

If we compare the DNA sequence of the given two species, we would find that three mutations have taken place.

Species A: CTTAAGCTAGTAAGGACC  

Species B: CATAAGTTAGTAAGGTCC  

Thus, 30 million years would have passed to evolve three mutations.

Hence, they must have shared a common ancestor around 30 million years ago.