Answer
Mitochondria and chloroplasts probably originated as prokaryotic cells taken up by eukaryotic cells, which then converted the prokaryotes into organelles. If this is true, the ATP synthases in the prokaryotes and the organelles should have similar sequences, showing the connection.
Work Step by Step
This question is asking you to connect the material in this chapter to earlier material about the origin of some eukaryotic organelles and to the use of DNA sequences in determining relationships among organisms (or, in this case, organisms and related organelles the ancestors of which were single celled organisms).