Comparing DNA sequences examines the relationship between different species. If the theory of evolution is supported, then species that share a common ancestor willl have inherited that ancestors DNA sequence. Any mutations will cause slight differences in species. The more alike two DNA sequences are, the more closely related the two species are. The more differences in the DNA sequence, the more time has passed since they had a common ancestor and the less related the species are now.
I hope this makes sense. I just copied out of a book lol
