Below are short fragments of DNA sequences from two yeast strains (A and B), which have been diverging from each other, as well as a short fragment from their common ancestor (C).
Yeast A: TGACTGCAAACATCCTAG
Yeast B: TGCCTGGACACATCGAAG
Yeast C: TGCCTGGAAACCTCCTAG

What is the minimum number of evolutionary changes that have occurred between the common ancestor and strain A?

Question

Below are short fragments of DNA sequences from two yeast strains (A and B), which have been diverging from each other, as well as a short fragment from their common ancestor (C). 
Yeast A: TGACTGCAAACATCCTAG
Yeast B: TGCCTGGACACATCGAAG
Yeast C: TGCCTGGAAACCTCCTAG

What is the minimum number of evolutionary changes that have occurred between the common ancestor and strain A?

Quizplus · Accepted Answer

Comparison of the sequences reveals three differences between A and C (TGACTGCAAACATCCTAG vs. TGCCTGGAAACCTCCTAG) and no differences between B and C (TGCCTGGACACATCGAAG vs. TGCCTGGAAACCTCCTAG). Therefore, strain A has diverged from the common ancestor through three evolutionary changes.

Below Are Short Fragments of DNA Sequences from Two Yeast