Question

he genomes of three species of mice are being sequenced, and a particular DNA sequence found in all three species is found to have a steady mutation rate. The sequence of interest for these three species is shown below.

Species A: ATTCGGATTATTCGAGG
Species B: GTCCGGTTCATTGGACA
Species C: ATCCAGATCGTTCGTGG

Which of the following inferences can be made, based on this information? (2 points)

	Species B and Species C most likely diverged from Species A since they both have more mutations than Species A.
	Species B most likely evolved from Species C since they are closest to each other in terms of number of mutations.
	Species A and Species C most likely share the most recent common ancestor since they differ by the fewest mutations.
	Species C most likely diverged from Species A more recently than Species B since Species C has fewer mutations than Species B.

Answer 1

Okay, so this sequence is being used a molecular phylogenetic marker, remember that such analysis will only tell wich species is more closely related to each other. Let us count the differences:

	A	B	C
A	0
B	7	0
C	5	8	0

This means species A and C are more closely related. We don't know which is species is the outer group for the other 2 because the tree is not rooted, what we know is that the common ancestor of A-C is more recent than the common ancestor of A-B or B-C.

The answer is the third option: Species A and Species C most likely share the most recent common ancestor since they differ by the fewest mutations