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

What you need to do is count up the differences in the two segments. (the mutations) Every time there is a different letter in the second segment, that's one mutation. Since one mutation occurs every 10 million years, multiply the amount of mutations counted by 10 million years. That's how long ago the two segments were the same, i.e., how long ago they shared an ancestor.

Answer 2

Yeah, I saw over like 3 differences, But I am not sure if I found the right differences, lol...
Where are the differences?

Answer 3

Species A: CTTAAGCTAGTAAGGACC
Species B: CATAAGTTAGTAAGGTCC
So would the differences be on the second letter A --- The 7 letter T And the 3 to last letter T???

Answer 4

For example, say you have a chain of DNA that reads GATTACA. If this chain follows the same rate of mutation as your example, a a new segment of DNA with TATTAGA shared an ancestor 20 million years ago.

Answer 5

Yes, you're right, those are the mutations. It's any difference in the chain order

Answer 6

So the answer would be 30 million years?

Answer 7

Yes, 30 million!

Answer 8

haha, Thanks a lot!