Question

Suppose a segment of mitochondrial DNA (mtDNA) is compared between two similar modern-day species. It is known that this segment of mtDNA changes at a steady rate of one base pair every 4 million years. Compare the sequences of the two mtDNA segments given below.

Species A: GCACTAAGCATCGATTT
Species B: GCACCAGGCACTGGTTC

Use the basic principle of molecular clocks to calculate how long ago the two species diverged from a common ancestor.

Answer 1

Here's a similar question. @Jhannybean

Answer 2

This is what I got:

\(6~differences \cdot \dfrac{4~million~years}{1~mutation} = 24~million~years~ago\)

Answer 3

Oh this is just doing the reverse process.

Answer 4

Is that one of the answer choices?

Answer 5

Yep.

Answer 6

12 million years ago
8 million years ago
48 million years ago
24 million years ago

Answer 7

And the others? They probably don't make sense, anyway.

Answer 8

So backtracking, last question we found the initial set of differences that was 5, but we needed 8.

5/80 = 1/16 , leaving us with 3 more differences.

Within an approximation of 80 years, we found about how many years it would take us to fully complete 8 change of bases.

Answer 9

With that we got what would be approx 48 years, right?

Answer 10

Yep.

Answer 11

So yes, I think your approach is correct.

Answer 12

Okay, thanks.

Answer 13

You're saying that it'll take 24 mil. years to make 6 changes, as compared to the 4 years to make 1 change in the sequence.

Answer 14

Yep.

\(Number~of~changes \times rate~of~mutation = how~long~ago~the~two~species\)
\(~diverged~from~a~common~ancestor.\)

Answer 15

Yeah :)

Answer 16

24 was wrong.. @Jhannybean >.>

I have no idea why.